Intake manifold modifications

[NoDOHC]

Ok, Vex has me thinking about this intake manifold thing now.

I have always been told that the RE Intake manifolds flowed the best. Not having access to a RE manifold, but having access to many Turbo II manifolds, I decided that i would make do with what I had.

After increasing the runner cross-sectional area from 2.32 in2 to 3.20 in2 (a lot of die grinding), giving the engine a mild street port (more die grinding), polishing the runners to 400 grit where dry and 80 grit where wet, measuring the entire runner length to maintain a uniform cross-sectional area in the manifold (don't ask how many times I broke through), modifying the plenum to fill all irregularities and smooth the air path, and porting and polishing the throttle bodies, I have encounted some odd engine characteristics.

(I polished the rotor faces to 1000 grit, but I doubt that had any effect on the power.) I am using stock S4 8.5:1 rotors (ground down to about 8.2:1)

I have yet to get on a real dyno, so I will not post numbers here except for AFR and VE (which I can compute) and relative torque (from the g-tech).

The VE for this engine is above 100% from 3000 rpm to 8500 rpm (9000 rpm rev limiter). I promised myself that I would stop at 8500rpm, but I couldn't cut an engine off that was pulling that hard. Unfortunately, my peak VE (108% at 6500rpm) is disappointing for me (I had hoped for 112% at 7000rpm).

The rev limiter is very annoying at 9,000 rpm because it is still pulling strong. (My legs are too important to me to rev it higher, my clutch is rated for 9500).

At 13.2:1 AFR, I can't keep my Bridgestone HP50s hooked up above 3500 rpm in first gear (with a gentle launch).

My first question: Would anyone find it beneficial if I strapped a stock TII manifold on the engine to see how much it kills the VE?

My second question: Why does my G-tech show the peak acceleration at 7500 rpm when the peak VE is at 6500 rpm? (Is there something I am missing, shouldn't peak torque and peak VE coincide?)

Is this a transient issue? Maybe the g-tech assumes a road load that is incorrect.

VE curve (based on injected quantity, injector size, fuel pressure and AFR as measured on the wideband):
rpm 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000
VE 67% 75% 78% 85% 95% 100%103% 103% 103% 104% 106% 106% 108% 107% 104% 101% 100% 94%
Torque curve: (Please do not set store by this, g-tech numbers assuming 3000 pound car weight, up to 10% high)
rpm 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000
lb-ft 130, 135, 145, 148, 152, 155, 156, 158, 158, 160, 163, 165, 160, 152, 140

For comparison:
NA 6-port, sleeves opened at 5000rpm, Stock intake manifold, secondary throttle plate mod.
rpm 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 7500
VE 75%, 80%, 83%, 89%, 91%, 95%, 93%, 89%, 82%
lb-ft 120, 123, 125, 128, 132, 135, 135, 128, 120
(made about 155 WHp with 196,000 miles)

I really need to make a real dyno run (I am actually excited because I think I can break 200 WHp.)

Also: What AFR do you guys typically run on a NA rotary? This thing LOVES fuel. Seems to make peak torque at 12.2:1 (my 6-port, 9.4:1 engine made peak torque at 13.5:1 AFR).

I have heard 26 degrees is optimal ignition timing, is this true for NA? I get best torque at 44 degrees BTDC at 9000.

Any thoughts are welcome.

[vex]

For your second question it sounds like the G-Tech has the incorrect numbers as you believe. It's a rough estimation based off G-Forces that the accelerometers measure when you accelerate. (If I'm assuming function correctly) If this is the case the formulation would work out that their assumed constants are incorrect and as such would need to be altered to match the more accurate reading of the dyno pull. However this also depends on your VE and how accurate that measurement is.

Your G-Tech by all means could be accurate and your reading of the VE could be off. As it stands your VE and your Max Torque reading are pretty close together. What you need to find out is how accurate your measuring tools are. Is your G-Tech able to measure max acceleration +/-500 RPM? Remember, 500RPM isn't that big of a discrepancy as we already miss 250 when our engines are off (aka our tach isn't reading anything below 500rpm)

Making any sense? I would first quantify the accuracy of the gauges/measurements independently and see if you can rectify any inconsistencies between them. Then, and only then would it become beneficial to measure the differences in VE, Torque, and RPM between the two manifolds.

[NoDOHC]

So basically, a dyno is really the only good option to optain this information (which unfortunately means that it will cost me $75 to find out).

I will have to postpone the dyno run until later as it seems that I have ruined my 4th transmission (I can't decide if it is torque or revs that keeps killing them). I still hope to get in there by the end of the summer.

I know engine RPM from the data logs for the ECU. I know Air fuel ratio and injection duration which should give me a good VE curve (this is all data logged). I would trust the VE curve ahead of the g-tech.

I don't believe the g-tech torque numbers. 150 wlb-ft will make me very happy. The relationship between the numbers is what I find odd.

[vex]

For torque, yes. Unfortunately that doese not resolve the inaccuracies present in the dyno itself. You may be off as much as +/-5% maybe even more. If the shop has it available, see the last time it was calibrated (if they even have it calibrated beyond first install). I'm going to do some digging on this and see which dyno actually gets calibrated.

Yeah, there are services that calibrate dyno's:
http://www.taylordyno.com/oth/oth.html?kc=googleppc&kw=dyno%20calibration&ex=8srfdn-eep549-10nhc1j&gclid=COeHvbff15sCFRwpawodOwR-_A

[NoDOHC]

Update:

Decided to do dyno run on junk transmission as the entire test would be done in fourth gear (direct - no torque is transmitted through countershaft - doesn't need good countershaft bearings).

Unfortunately, when told that the engine turned 9,000 rpm and that the rear tires would be going 180ish MPH in fourth gear the dyno guy told me that a third gear run would be all I would get.

I was worried if the tranny would take it, but I figured we could always tow it home, so I let him run it in third.

I was very dissapointed with the output (186.9 WHP at 7200 rpm). I have a lot of tuning to do.

I learned that my gut feeling for ignition timing was not accurate as I started with 62 degrees BTDC at 9,000 with 13.8:1 AFR (gave 169 WHP at 8200).

Retarding the timing to 52 degrees BTDC at 9,000 gave me 182 WHP at 7100 rpm

Adding fuel to 13.2:1 gave 186 at 7200 rpm.

I think peak torque can be found at a more retarded ignition angle (as I was still increasing torque by retarding). I think peak torque is somewhere between 13.8 and 13.2AFR, but I will still try going a little richer. Peak torque (172 Wlb-ft) was made at 4800 rpm and it was running a little fat there (12.2:1).

Still hoping for 200 WHP as my high end is currently wasting fuel (>100% VE) and making no power. My spark plugs are filthy (too much premix) and will be replaced before the next dyno run.

More dyno runs later (the transmission is still alive!!)

On a side note, this is a Mustang Dyno and it has steady state loading, so I can actually tune real time (although I should get an electric fan to keep the engine cool during a steady state run at 8,000 rpm).

Comments/suggestions welcome (I will be renting the dyno for several hours this coming weekend, so I can try about anything).

[vex]

Rule of thumb 12:1.

[RotaryProphet]

Update:

I learned that my gut feeling for ignition timing was not accurate as I started with 62 degrees BTDC at 9,000 with 13.8:1 AFR (gave 169 WHP at 8200).

Retarding the timing to 52 degrees BTDC at 9,000 gave me 182 WHP at 7100 rpm


It's also really -really- far advanced from what I've heard of anyone running, even up at the redline. If you got 13WHP from retarding 10 degrees, I'd say you're way advanced. On an NA 13b, while on an engine dyno, I've never had to advance past 40, and that was a motor that was already on the down-slope of the VE curve. I seem to make pretty good power on most port configurations around 30+/-5 degrees BTDC.

Something to remember is that as you increase airflow to the chamber, you need less spark advance, not more. Retard your timing out towards the stock numbers, and you probably will hit 200whp

[NoDOHC]

If I really wanted 200 WHp, I would take my mechanical fan off. I think that it is single-handedly hurting my high end. You should hear it scream on the dyno, sounds like a jet liner. If I could get this mark IV fan to fit I'd have it made.

Thanks for the advice guys, I will give it a go on Saturday.

[RotaryProphet]

If I really wanted 200 WHp, I would take my mechanical fan off. I think that it is single-handedly hurting my high end. You should hear it scream on the dyno, sounds like a jet liner. If I could get this mark IV fan to fit I'd have it made.

Thanks for the advice guys, I will give it a go on Saturday.

In that case, also check your fan clutch. =cP

[drewski86]

(I polished the rotor faces to 1000 grit, but I doubt that had any effect on the power.) I am using stock S4 8.5:1 rotors (ground down to about 8.2:1)

Are you eventually going to turbo this motor?

Would anyone find it beneficial if I strapped a stock TII manifold on the engine to see how much it kills the VE?

It would be nice to know how much porting the manifolds really helped.

Why does my G-tech show the peak acceleration at 7500 rpm when the peak VE is at 6500 rpm? (Is there something I am missing, shouldn't peak torque and peak VE coincide?)

Peak acceleration should coincide with peak power.

186.9 WHP at 7200 rpm

See

I learned that my gut feeling for ignition timing was not accurate as I started with 62 degrees BTDC at 9,000 with 13.8:1 AFR (gave 169 WHP at 8200).

Retarding the timing to 52 degrees BTDC at 9,000 gave me 182 WHP at 7100 rpm

Something is wrong. You should be more around 25-30* BTDC. As far as you are advanced, you should be igniting on the compression stroke which will want to spin the motor backwards which is very bad. Hopefully your numbers are off somehow. I would make a pull at 25* and 13.1 AFR and see what happens. If you're way down on power than maybe your numbers are off but the motor is seeing the correct timing.

One more thing, you seem too focused on torque numbers. I don't know if this is because the g-tech only gives torque numbers but horsepower is what makes the car fast.

[NoDOHC]

Are you eventually going to turbo this motor?

I definately intend to put a turbo on the engine. In fact, it should be turboed right now, I was only going to run it 3,000 miles (breakin) and then add a turbo. I have over 5,000 miles on it and I still haven't found a good deal on a dual-disk turbo clutch (I refuse to deal with a 6-puck, I drive this car every day). I have a stock clutch in my garage, but I don't have the ambition to take the engine out twice and the stock clutch will never take 15psi boost (I have NA drivetrain in the car for now, will put the turbo drivetain in in one swoop).

If I was staying NA, I would have used 9.7:1 rotors (which I have been accumulating for years) and I would have given the engine more port overlap when I streetported it. I certainly would not have polished the rotors to the extent that I did, either.

Peak acceleration should coincide with peak power.

You are right, peak acceleration should coincide with peak torque. The G-tech measures acceleration, thus it displays torque. It is not that accurate however, as the dyno run would indicate.

It's also really -really- far advanced from what I've heard of anyone running, even up at the redline. If you got 13WHP from retarding 10 degrees, I'd say you're way advanced. On an NA 13b, while on an engine dyno, I've never had to advance past 40, and that was a motor that was already on the down-slope of the VE curve. I seem to make pretty good power on most port configurations around 30+/-5 degrees BTDC.


Something is wrong. You should be more around 25-30* BTDC. As far as you are advanced, you should be igniting on the compression stroke which will want to spin the motor backwards which is very bad. Hopefully your numbers are off somehow. I would make a pull at 25* and 13.1 AFR and see what happens. If you're way down on power than maybe your numbers are off but the motor is seeing the correct timing.

The timing is my fault, I knew that the rule of thumb was 26 degrees, but I thought that the engine seemed to pull harder at 60 degrees. I think that it must have made more noise and maybe shook a little more, which seemed like power to me. The dyno is definately informative and a great learning experience for me.

One more thing, you seem too focused on torque numbers. I don't know if this is because the g-tech only gives torque numbers but horsepower is what makes the car fast.

As to horsepower making a car fast... I will have to disagree on that one. My Rotary makes about 230 Hp, I have a friend with a 302 Ford in an RX7 that makes 230 Hp, that car is WAY faster than mine (the only difference is torque 210 lb-ft vs 360 lb-ft).

I like torque because it indicates the engine's Volumetric efficiency and combustion efficiency. You can always get more horsepower by porting more overlap and revving the engine higher, but you have to do careful tuning to get more torque.

Basically, my car makes 210 lb-ft of torque at the flywheel. Compare that to a stock 88 TII and you will see what I am talking about.

My goal is not to make a watchwinder, but rather to make a daily driver that has lots of low end, is very driveable and will still accelerate very quickly if it needs to (about 6 seconds 0-60). The total power number is not as important as what I learn and how pleasant the car is to drive.

Since I am stuck NA for a while, I figured I might as well benchmark it and see what it would do.

The timing that I am listing is definately right, I had a degree wheel on it.

In that case, also check your fan clutch. =cP

I know the fan clutch is bad, the car was referred to as the airplane at autoXs because all you could hear was the fan (I have the '91 for autoXs now, factory electric fans are awesome). I would take it off, but I think that is cheating, so I am leaving it (that and I don't want to overheat).

This may sound stupid, but I don't care what the number I put down is. It really isn't important, All that I care about is what kind of power it made NA so that I can baseline it against the turbo numbers. If I hadn't been seeing such increases last time at the dyno, I would have been happy with one $70 expense and called it 186 WHp.

[vex]

One more thing, you seem too focused on torque numbers. I don't know if this is because the g-tech only gives torque numbers but horsepower is what makes the car fast.

That is a negative. The true meaning of HP is the application of Torque over time. This means that 1 HP = 550Ft-Lbs/sec.

[C. Ludwig]

As has been pointed out your timing was advanced way too far. I would start at 25* and creep up from there. All of my NA experience is with 6-port 9.7:1 engines so your results may wary slightly. You would expect the lower compression ratio to want slightly more timing as well as a slightly fatter mixture with similar VE. If you can increase the VE a lot over what we can do with the 6-port and higher compression the timing could be very similar. At any rate, start low and work up until you stop gaining power. As you have seen already, in an NA form it's pretty much impossible to detonate one of these engines unless you have other problems.

The same goes for fuel. We've always found best power in the 13.5:1 area. Going fatter certainly has lost power. Whatever the conventional theoretical optimum a/f ratio is has not applied. Again, start fat and pull fuel until you reach a point you are comfortable balancing EGT and power.

What are you doing for exhaust?

It's probably moot but if you have a bad counter shaft bearing you're still spinning against that friction even in fourth gear. You might not be loading the counter shaft but the friction could be costing you several hp depending on how bad it is. And how big are your tires? No way you're doing 180 mph in 4th with a 4.10 rear gear. More like 130, maybe 140 with very tall tires.

Be extremely careful if you plan on doing full load, high rpm steady state tuning. The loading on the engine is quite dramatic. Something it will not see in real life. The heat build up is quite fast. You will literally get a couple seconds at full load to see what's going on and get an idea of what changes you need to make. You are not going to fully load the engine and sit there and make ignition adjustments and watch torque feedback in real time. You can do this at lower rpm but not at 8k regardless of what kind of fans you're using.

[drewski86]

That is a negative. The true meaning of HP is the application of Torque over time. This means that 1 HP = 550Ft-Lbs/sec.

You're right, horsepower is work(torque) over time, but that does not mean that horsepower is an irrelevant by product. Let's put NoDOHC's friends V8 RX7 vs an F1 car. The V8 makes 230hp and 360tq whereas the F1 car makes 800hp and only 200tq. Do you think the V8 will win because it makes 160 more foot pounds of torque? You would be wrong. Torque IS work, but horsepower DOES work. Here is a saying that puts it in perspective. "Horsepower is how fast you hit the wall. Torque is how far you take it with you."
You may want to check this site out.
http://www.vettenet.org/torquehp.html

You are right, peak acceleration should coincide with peak torque. The G-tech measures acceleration, thus it displays torque. It is not that accurate however, as the dyno run would indicate.

No it should coincide with peak horsepower, not torque. You said the G-tech showed peak acceleration at 7500 RPM and the dyno showed peak power at 7200 RPM. This is your own data that proves this as fact.

As to horsepower making a car fast... I will have to disagree on that one. My Rotary makes about 230 Hp, I have a friend with a 302 Ford in an RX7 that makes 230 Hp, that car is WAY faster than mine (the only difference is torque 210 lb-ft vs 360 lb-ft).

That's because the V8 has a much broader powerband. I'm sure if you compare dyno sheets you will see this as true. Peak numbers don't win races, area under the curve does.

[C. Ludwig]

You're right, horsepower is work(torque) over time, but that does not mean that horsepower is an irrelevant by product. Let's put NoDOHC's friends V8 RX7 vs an F1 car. The V8 makes 230hp and 360tq whereas the F1 car makes 800hp and only 200tq. Do you think the V8 will win because it makes 160 more foot pounds of torque? You would be wrong. Torque IS work, but horsepower DOES work. Here is a saying that puts it in perspective. "Horsepower is how fast you hit the wall. Torque is how far you take it with you."
You may want to check this site out.
http://www.vettenet.org/torquehp.html


You're ignoring gearing in your comparison. Gear the F1 car with the same gearing that would be optimal for the high torque engine and it will be a slug. What makes any car go is torque at the wheel. The F1 car needs a very short gear to extract it's power potential and allow it to use it's 20k revs to create torque at the wheel through gear reduction. Use the F1 correct gearing with the low hp/high torque V8 and, if traction is available, it will murder the F1 engine up to the point it runs out of revs which would happen very quickly.


No it should coincide with peak horsepower, not torque. You said the G-tech showed peak acceleration at 7500 RPM and the dyno showed peak power at 7200 RPM. This is your own data that proves this as fact.

Peak VE will always coincide with peak torque at the crankshaft. Peak VE is the point at which the engine is operating at it's peak efficiency and will create the most torque at the crankshaft. Peak horsepower is a product of torque and rpm. VE will fall past peak torque but if it's maintained at a high enough level the engine will continue to gain horsepower due to the multiplier of rpm. This is why most engines will have a torque peak at a lower rpm than their horsepower peak. You will see this in fuel curves, as NODOHC has mentioned, with fuel injector pulse width required to maintain a common a/f ratio rising up to the point of peak VE and then beginning to fall past peak VE as airflow falls.


That's because the V8 has a much broader powerband. I'm sure if you compare dyno sheets you will see this as true. Peak numbers don't win races, area under the curve does.

Broader than what? A stock 6-port engine will maintain 90% of it's torque for around 4500 rpm. Most stock V8s on the road hardly rev that high let alone maintain torque across that kind of rev range. One of the nice properties of the NA rotary (even boosted for that matter) is that they have nice flat, broad torque curves.

Stock S5 NA

http://ludwigmotorsports.com/work/mod_dyno.jpg


Boosted semi-PP

http://i383.photobucket.com//albums/oo279/awdmotorsports/alandyno32.jpg?t=1230857756


Stock 2008 Mustang GT v. w/CAI

http://image.mustang50magazine.com/f/9318722+w750+st0/m5lp_0802_08_z+2008_mustang_GT+dyno_graph.jpg

[drewski86]

You're ignoring gearing in your comparison...

This is starting to make sense. For some reason, ever since I was a kid I looked at x amount of horsepower meaning x amount of horses available to work and more horses can obviously pull something faster. I wasn't taught this, it's just how it made sense to me as a kid.

[vex]

This is starting to make sense. For some reason, ever since I was a kid I looked at x amount of horsepower meaning x amount of horses available to work and more horses can obviously pull something faster. I wasn't taught this, it's just how it made sense to me as a kid.

An easy way to think about it is this. It takes Horsepower to accelerate a car to a specific speed. Depending on where you are in the RPM band you are applying a certain amount of torque at that instant to the ground.

If you've taken a dynamics class in college or have yet to (I highly recommend it, it's one of the most confusing, hard, and most rewarding I have taken thus far) you will learn that to accelerate a car from 0-60mph in a certain amount of time takes some amount of horsepower. Maintaining 60mph takes significantly less hp. Accelerating above 60mph takes much much more than it did to go to 60.

That's more however due to wind resistance then overpowers rolling resistance. But just something to remember.


Torque is only good if the object doesn't move. IE: The wheel applies 90ft-lbs of torque at some point in time. Proceed a little further in time and you may be applying 200ft-lbs.

For this reason dyno's are able to calculate both at the same time since they're both relative and related to each other as previously attested.

If you'd like I could write up a little dynamics example about a car if it will better illustrate the point.

[NoDOHC]

On my tired 6-port, I made peak power at 6200 (155 WHp) this was at 13.5:1

It made 140 Wlb-ft at 3200 rpm.

I am impressed with the 4-port power.

My 6-port experience was what led me to tune around the 13.5:1 region. However, I can believe that my polished intake runners, smoothed ports and polished rotors will require a little more fuel.

I appreciate the advice everyone, I certainly hope that the transmission holds together for this pull.

I should be able to get dyno plots this time. Last time the rpm trace blinked out at about 5200 rpm (I computed horsepower rpm from wheel speed).

Believe it or not, at 9,000 rpm in 4th gear, the rear wheels are actually going 180 mph - not that I have gone that fast, but the engine is running exactly 4,000 rpm at 80 mph (I have checked the speedometer and the rpm is from the Haltech).

The Dyno guy wouldn't run it in fourth.

I know I may lose something to bad bearings in fourth, but the friction must be higher when the bearing is experiencing a side load as the power is transferred through the input gears in 3rd gear (thus 4th gear would be better).

I did check the transmission temperature between runs and it was not touchable, but not smoking yet either.

[C. Ludwig]

On my tired 6-port, I made peak power at 6200 (155 WHp) this was at 13.5:1

It made 140 Wlb-ft at 3200 rpm.

I am impressed with the 4-port power.

My 6-port experience was what led me to tune around the 13.5:1 region. However, I can believe that my polished intake runners, smoothed ports and polished rotors will require a little more fuel.

Doesn't really work that way. You're trying to provide just enough fuel so that every oxygen molecule has something latch on to. You'll hit peak efficiency when you use all of the oxygen molecules without wasting a bunch of fuel. Stoichiometric is the theoretical mixture at which all of the oxygen available find a fuel molecule to work with and all the fuel is burned up. You usually find max torque in the real world at a mixture on the fat side of stoich because in a combustion chamber things aren't ideal. A good intake system and combustion chamber will allow for proper mixing (tumble and/or swirl of the charge) and proper quench to keep the charge more or less packed into a homogeneous mixture near the plug. A good combustion chamber will also promote good flame propagation which helps to ensure the entire mixture is burned. If you need a mixture that is fatter then you've lost efficiency somewhere. It's possible you're seeing peak torque at that mixture but if you are something has changed to the detriment of efficiency. You're still not making more power than has been made with completely stock components so if it's taking more fuel you've erred somewhere.

Believe it or not, at 9,000 rpm in 4th gear, the rear wheels are actually going 180 mph - not that I have gone that fast, but the engine is running exactly 4,000 rpm at 80 mph (I have checked the speedometer and the rpm is from the Haltech).

I absolutely don't believe it. I spent a number of year racing these car in SCCA Club Racing. I know how fast the thing goes in 4th with a 4.10 rear gear. Even a gear calculator will tell you that you're well short of 190 mph. Just ran through one and it gives 150 for a 23" tire and 163 for a 25" tire. That's higher than I said before. Guess I was thinking 8k max rpm which was typical at most tracks we ran at. Unless you have a 30" tire on there you aren't seeing 190. They don't call them dreamometers for nothing.

[NoDOHC]

C. Ludwig - You are my new hero. I think I can safely run in fourth gear. I ran the numbers and you are right. I guess my speedometer is wrong then (I timed it between milemarkers... I thought it was right). Maybe the curve will be more accurate in fourth, plus my transmission will not take as much of a beating.

Thanks for pointing that out. I should have done the math (especially since I looked at the VSS input to the Haltech and it indicates 55 mph at 3000 rpm, not 60 as I thought). I guess this is good, I don't need to worry about a speeding ticket...

With my new knowledge, my power numbers shifted.

It is now 186 WHp @ 7600 rpm
and 170 lb-ft @ 5100 rpm

(we had calibrated the dyno to the speedometer for rpm).

You are right about the efficiency too, I doubt that my highly polished rotors and runners do much for my fuel mix.

I did drive it hard a little today with a wideband on it and I found that it seems to pull just fine at 13.5:1 (Which is what I am currently tuned for). I am running lean of that between 5000 and 7500) just because the VE is higher in that range and I copied and pasted the fueling from 3500 rpm. The tune is identical to what I ran on the Dyno. I only got an average AFR from the dyno, as the rpm signal was wacky. Apparently I was running a bit rich down low (11:1 at 1200 rpm). Leaning the low end out helped with the load up issues at idle.

We will see tomorrow (assuming that my new-found vibration doesn't disqualify the car from the dyno).

[NoDOHC]

Update:

Right before the scheduled pull, I lost my leading plugs. I didn't have time to troubleshoot what had happened (corrupted something in Haltech trying to get a Tacho output working). I went anyway, as I was not willing to miss my appointment.

With no leading plugs, the car starts hard and has no low end (I didn't know why at the time).

Interestingly enough, the high end was fine.

First run of the day was 163 WHp and 123 lb-ft (13.8:1 11 degrees of timing (which I thought was 26, but I had the trailing plugs only)

Richened it up to 12.8:1, went to 181 WHp and 142 lb-ft

Gave it 10 degrees of timing (21 BTDC) went to 198 WHp 150 lb-ft

Richening to 12.2:1 and giving another 5 degrees (26 BTDC) gave 201.3 WHp and 150 Lb-ft

Made 3 runs at 12.2:1 and adjusted the timing around 3 degrees in either direction yielded 200.6 WHp and 203.2 WHp.

At this point, my clutch was starting to slip and I was running out of time, so I had to head home. It is really a pity that I had no leading plugs, as this would most likely have helped my low end torque.

Sadly, I probably won't dyno this car again until I get the turbo on it.

Dyno plots are yet to come.

[NoDOHC]

I finally got the dyno plots scanned in. I deleted the header (for obvious reasons).

I don't know why the dyno scaled the horsepower and torque to different levels. The last one I actually got them to drop air/fuel just so that I could see both scales.

[NoDOHC]

I must remove some misinformation.

Later analysis of my wiring on my car has proven to me that I had to have operational leading spark plugs for the dyno run. This indicates that I really was making peak power at 38 degrees BTDC (203 WHp run).

Looking at the curves, I think I should have run a little leaner for peak power too. If It didn't cost so much to go to the dyno, I would do another run to see if I could sneak another 10 WHp out of this build.

Maybe I will go back after I get my clutch fixed and I can run the stock manifold too.

Information Summary:

Polished rotors seem to require more ignition timing (38 BTDC)
Low compression (8.2:1) is probably another part of it.
Lack of swirl in intake manifold due to excessive polishing requires additional fuel (Probably 12.5 - 12.8:1).
Even so, 460cc/min injectors are PLENTY for 200 WHp (69% duty cycle at 7100 rpm).

I really want to thank everyone for their input. It helped me to get a sanity check. It also allowed me to get a feel for typical timing and fuel requirements so that I can estimate what effect the changes I made had on the engine operation.

After I blow this engine up with too much boost :) I have every intention of building a HOT 6-port (custom intake manifold) that will have much more radical port timing and 9.7:1 rotors.

I am puzzled about one thing - Why is my high end missing?
It can't be VE, here is my -5 kPA Injection time map (I run about -3.75 kPA at 2500 and -6.75 kPA at 9000. I have also included this data as an excel file (inside the .zip).
2500 4.53
3000 4.73 (rich spot on scan0005)
3500 4.53
4000 4.83
4500 4.93
5000 5.21
5500 5.31
6000 5.53
6500 5.72
7000 5.83
7500 5.83
8000 5.65
8500 5.41
9000 5.10

Running the numbers, I find that I should make a lot more power at 8500 than I do at 7500, why does it taper off?

Any input is appreciated, as I am surprised by the VE being 115% (giving me more torque than I expected) but I am disappointed with the engine's high rev performance.

Please review the attached spreadsheet for errors, but I don't understand why I am seeing this drop in combustion efficiency after 7000 rpm. I can only think ignition timing, but I did not have enough dyno time to do anything with it.

Any input is appreciated!

[C. Ludwig]

Good power!

The oversimplification is that the air flow is not there for high end power. Whether it's intake or exhaust the package as whole isn't flowing past 7500.

[NoDOHC]

I found some issues...

First, the ignition toggle output pin had come out of the Haltech the last time I had the plug apart. This caused my rear rotor to receive all of the ignition for the trailing plugs (which made the car start hard, it kept kicking back on the starter).

At 38 degrees BTDC, the apex seal is just crossing the leading spark plug. Thus I had very poor ignition on my front rotor without the trailing plug firing.

I lost the ignition driver for the leading plugs on the Haltech (by a stupid testing procedure on my part) and this allowed me to discover this problem. Imagine my worry when the engine only ran on one rotor.

A compression check yielded 120 psi on both rotors (5,300 miles on rebuild) so I knew that it wasn't a mechanical failure.

After fixing the ignition toggle output, the car idles smoothly enough at 700 rpm that I think you could balance an egg on the intake manifold and it would stay there (or at least close).

I didn't show the curve that high, but I was at 110 WHp at 9,000 rpm (which is REALLY low) I think now that I was only running on one rotor by that point, the fuel in the other rotor was getting lit during the expansion stroke (So the wideband was none the wiser).

Unfortunately, the other issue I found was that I need a turbo clutch. My NA clutch was slipping during the last dyno run and after I got out on the road (and got intake air temps below 40C) it wouldn't hold at all at full throttle.

I finished it off trying to keep up to my friend in his hopped-up Duramax.

I could barely get the car to move by the time I got home from the dyno.

I will keep you posted when I get the chance to run again. I am hoping that I can make better power.

[C. Ludwig]

I've run 300 whp through Miatas which have the same clutch disk as the NA RX-7. If you're upgrading to turbo components anyway then by all means do the swap. But a good small diameter clutch will hold well more than you're throwing at it.

[RotaryProphet]

I've used the NA style centerforce dual friction clutch to very good effect on a 240rwhp turbocharged 12a and a 230rwhp bridgeport NA, and it even managed to hold up to 315rwhp on a turbocharged bridgeport (although admittedly, I stopped streeting that setup after only a couple of weeks of driving it)... meanwhile, the clutch engagement is very smooth, and pedal pressure is near to stock.

[NoDOHC]

This was a cheap F1 racing clutch from eBay. The purpose was to hold until I went turbo, so I didn't figure it mattered. I think it would have been ok, but my master cylinder leaks off over time and sometimes the pedal will stick partway down with the clutch only about half engaged. I think this happened to one of my friends when he was driving the car, the pedal effort was significantly decreased when I drove it next (I think that the pressure plate got hot enough to partially anneal the engagement springs).

I intend to remove the engine soon (I can't drive the car anyway) and see what I can see.

I got the F1 racing clutch mostly for the rev rating (9500 rpm) which I figured was all my engine could safely do. Now that I have trailing ignition for both rotors I expect to need that rev rating.

If I had intended the car to end up as NA, I would have purchased a better clutch. I have a stage 3+ SPEC clutch (505 lb-ft rated) and a billet steel 10 lb flywheel for the turbo build.

If I ever get the time and ambition, I will install the turbo drivetrain in the car.

[NoDOHC]

Update:

Got the new clutch (It looked pretty neat, I may get some pictures up later).

Installed Turbo drivetrain in the car.

Pedal effort is a little high, but the engagment is very smooth (as long as you don't try to drive gently).

The new tranny is excellent (has synchros in all gears!!)

After I finished with the drive train swap, I decided to take the car to the dyno again (more money...)

Unfortunately, I had to give up my easy turning transmission, my ultra-lightweight flywheel, etc so I figured that I would lose a couple wheel horsepower.

I was happy as a clam when I put down 203 WHp and 152 Wlb-ft of torque on my first run (Identical numbers to last time). I then decided to adjust the ignition timing some more.

Here is a summary of what I found
Ignition Advance at 8000 (Degrees BTDC),Peak Power,Peak torque
38,203,152
43,198,154 (I think the torque was inaccurate)
33,198,148

So now I decided to try fueling.
AFR (Average),Horsepower,Torque
12.5,203,152
12.8,210,155
13.0,216,158
13.3,216,160
13.8,200,145

Going back to 13.3:1 I started adjusting trailing split
Trailing split (degrees),Horsepower,Torque
15,216,158
10,216,158
5,216,159
0,216,160
-5,212,157 (I swapped leading and trailing plug wires for this test).

So peak power was 216.4 WHp at 7575 rpm and 160.2 Wlb-ft at 6100 rpm w/ 38 BTDC timing, 13.3:1 AFR,0 degree split.

(The glitch in the air fuel chart was corrected later, but after the AFR was steady, we quit including it on the trace.)