Intake manifold modifications

[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.

[drewski86]

Originally Posted by vex

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

Originally Posted by NoDOHC

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]

Originally Posted by drewski86

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.

Originally Posted by drewski86

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.

Originally Posted by drewski86

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




Boosted semi-PP




Stock 2008 Mustang GT v. w/CAI

[drewski86]

Originally Posted by C. Ludwig

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]

Originally Posted by drewski86

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.