Boost falling off
 

Relevant mods

90 S5 Vert.
JDM Tii
Pineapple Racing street port
BNR Stage1 turbo
Bonez cat-forward. Corksport cat-back with Vibrant UltraQuiet resonator.
RTek Stage2
720/1000cc injectors
Zeitronix w/b
HKS EVC Black Edition

With the EVC off, we were seeing a max of about 4.5psi so I'm assuming the wastegate spring is about 4.5pounds. We set the EVC to 50% and we were expecting about 7psi max (4.5 + (50% * 4.5)) but it went to ten; which was fine.

As you can see in the Zeitronix chart, boost is maxing out at ~10psi at 4700RPM and drops off gently from there.

http://i366.photobucket.com/albums/o...ng/Turbo10.png

We are using Aaron Cake's rule of thumb AFR tuning targets

0-4 PSI: 12-12.5
4-8 PSI: high 11s
8 - 15 PSI: mid to low 11s
16 PSI +: high 10s

but obviously the 1000cc secondaries still need to be pulled back some. IIRC we are pulling them back about 3% above 4500RPM.

Is the fact that we're getting too rich after 4500RPM what's causing the boost to fall off or is the wastegate spring at fault?

Thanks, appreciate any guidance yall have.

Aaron Cakes "rule of thumb" AFR's are stupidly rich. I wouldn't follow anything of what he says.

More important, what are your timing numbers like?

The boost will fall off in the higher revs... this is just fact.

1) Get an EGT gauge
2) Learn how to tune with EGT
3) You're running too rich - too much fuel suppresses boost
4) Stop listening to Cake's bullshit


-Ted

QFT!!!!

:D

So instead of tunging using target AFR's you are sugguesting using EGT's...?

I thought (assumed) it was more accurate and "safer" to tune via AFR's not EGTs

input from both You Ted and Bryan would be great, as I am trying to increase my knowledge to when I decide to start trying to tune..


J

:squint:

EGT's will help you dial in the timing. For the people that have been doing it a long time, they can get damn close to target AFR's with EGT's

Wow! That's a lot of vitriol thrown Aaron's way.

I should have explained our goals and constraints. The car is my 21 year old's DD and all it needs to do is provide him fun, entertaining transportation until he graduates college. If it blows up and burns to the ground the second he receives his diploma then it has served its purpose.

It will never be raced but we don't want it so neutered as to simulate a soulless but infinitely reliable Corolla. Since we rebuilt the PoS Tii we got from TigerJapanese 3 years ago the car has run nicely at stock boost with an SAFC to fatten up the top end of the range.

Then in Oct'10 the turbo died and I had BNR rebuild it and had him do a Stage1 since it was just a bit more money.

Then in July'11 the SAFC died so I got the RTek 2 upgrade (from a 1.8) installed as it was cheaper than buying another SAFC and had more tuning headroom.

Over the winter I took the HKS EVC out of my 17 year olds MR2turbo and just ran it off the Tial's 12# spring since he doesnt need any more than that much boost. I believe that the FC's boost solenoid was lame because we were only seeing about 4.5 lbs of boost and when the ignition was on that solenoid would often buzz. So we put the HKS in the FC a couple of weeks ago and just this weekend turned it on and did a little street tuning; starting fat and leaning it slowly.

So we are not looking to tune it within an inch of its life, not looking to drag race it, not looking to spend any money, not looking to search for a pro tuner who knows rotaries and is willing to touch an RTek. Just want to find a reasonably reliable, reasonably fuel efficient, reasonably performant DIY street tune that will get him to and from school and will pass TX emissions and inspections.

Given that the stock turbo is frequently taken to 12psi I figured we'd set Mode A to 10PSI for daily driving and Mode B to 14psi as Brian@BNR said the Stage 1 was good to 1Bar.

On the RTek we are using the default Fuel Correction Map configuration. I have neither the skill to mess with rotary ignition timing nor the interest in learning. It is hard enough to find rules of thumb like Aaron's AFR and I have never seen a HowTo for tuning a rotary with EGTs and timing. And unfortunately the price of being a little tiny bit wrong is a blown engine with destroyed rotor housings.

So my take-aways from the replies are:

1. Aaron's AFRs are conservatively rich but no one has an alternative recommendation (except for buying EGT gear)
2. We are running richer than Aaron's already rich #s and that will impede our ability to boost
3. That richness may be why we max out at 10psi whether at 50% or 75% on the HKS.

Cool. We'll lean it out some more and see if that removes the 10psi ceiling.

Thanks,

Jim

For a relativley stock turbo and motor, you can be in the mid to high 11's at 10psi, even 12 flat.

There will always be some taper in boost with the stock turbo, it just can't hang in the upper rpms.

:rofl: I run 11.7 @ 17psi... and @ 1br I'm running about 12 flat. Then again... my ECU is a little more exact and responsive than an Rpuke.

Cake really shouldn't be listened to when it comes to certain/most things alot of people with violently disagree with. Why some people have their rantings taken as gospel and looked at as rules of thumb is beyond me.

Seriously though, is there anyway you can post up a timing map? I'm willing to bet there is a TON more power to be had out of your setup.

The thing that alot of people don't realize is that you can be so far into the so-called "safe-zone" that it actually becomes dangerous and will pop your engine.....

I refer you once again to 13B-RE Nova who had a thread in the single turbo section entitled.... why did my engine blow.

Basically he was running low to 10flat AFR's @ 21psi and 6*'s of timing making a whopping, earth rotating 427rwhp on a GT42 or 45....... oh, and it was HBP'ed.... anyone care to take a guess why he popped his engine and why hc and bdc are totally and completely WRONG and stupid for suggesting that all he needed was colder plugs?

^ most def, timing too retarded and afr's too rich can cause just a many probs as lean and way advance. def try to pull the leading and trailing maps off the rtek and post them up please!

We havent touched the timing maps at all.

I've been using the Zeitronix for logging boost, TPS and AFR but I believe I can log the boost, RPM, and the timing via the RTek PocketLogger. Havent played with that at all.

I'll try saving the configuration and see if the file is sync'd to the PC. That would have the stock timing maps in it. I know ARGHX tried getting the timing maps but it is tedious and so from what I can tell never happened.

We'll give it a go later this week or this weekend.

The Rtek Pocketlogger SW can log basically everything that the stock ECU uses as an input sensor, (i.e., MAP, intake temps, TPS, etc.) plus it has a spare input line that can be configured to log a wideband O2 sensor (0~5V, that you supply).

WRT timing maps, the Rtek simply lets you directly overwrite whatever data is stored in the stock maps (in degrees). In other words, be very careful here because the consequences of a fat finger error can be severe, especially if you didn't keep track of the stock settings before making changes.

The kid returned from class so we went out and did a quick third gear pull. It is currently 67 degrees and 60% humidity and we are at 600 feet elevation.

The RTek log display program is not especially impressive so I took four screen shots at different points so you could see the numbers. The app ignores any attempt to change the color of timing series so I left them in separate bands. Probably makes it easier to see anyways.

http://i366.photobucket.com/albums/o...ng/Timing1.png

http://i366.photobucket.com/albums/o...ng/Timing2.png

http://i366.photobucket.com/albums/o...ng/Timing3.png

http://i366.photobucket.com/albums/o...ng/Timing4.png

Again, these are all stock timing values.

Thx

According to turbo2ltr on the other site "With the Stage 2.0, to go back to nearly completely stock, you can initialize the ECU from within the software and, poof, you are stock again."

Course hopefully that's before :puke:

I hate to say it, but she really needs to be put on the dyno. Those afrs are way to rich, and the timing seems to be a little weak. Not to mention the split seems like it needs to be tightened way up too. We generally run 10* split in boost, not 20, if im reading that right.

If you're wanting to only mess with the fuel, set it for 12.5 @ 0 psi, 12 by say 7 psi, and nothing richer than 11.7

Yeah I read the thread on the single turbo forum you mentioned and I dont think they like you very much. :nopity:

Both Brian Cain (BDC Motorsports) and Steve Kan are in DFW so if the kid wants to spend the $400 he's welcome to do the dyno thing! It's only a 3 hour drive and he can go to In-N-Out for lunch. Course he'd have to call and make sure they'd be willing to contaminate themselves by touching an RTek.

We'll lean it out and see what happens. The preset is for 720/720 and we have 720/1000s and we added fuel across the map above 6psi just to be sure we weren't lean.

We'll get the AFRs in line and then we'll come back and ask about timing.