NA Lean Tip in.

[Shorty]

How about slightly bumping the fuel pressure and leaving the MAP where it is?

I'll preface this with "I don't know what the answer is, but..."

short term, the increased fuel pressure would probably work, but I would assume a properly functioning O2 sensor and ECU will see the "too rich" mixture and start to pull fuel from the motor.

I might try a longer arm on the throttle body to slow the rate that it opens. I know it isn't the best solution, but a proper mixture into the engine with a little slower throttle opening will probably run quicker than more air without fuel to compensate for it.

 

[cruiser54]

It may not be too rich but just right. Let's try it.

 

[Shorty]

I know the ECU goes "too rich" with wide open throttle, maybe if it's "tuned" for just right WOT ratios, it's doing what it should when still in closed loop?

If that's the case, a bit more fuel pressure or a bit lower MAP signal might help the closed loop throttle response, no?

edit-- I think I'm agreeing with you, but I'm not sure

 

[cruiser54]

I know the ECU goes "too rich" with wide open throttle, maybe if it's "tuned" for just right WOT ratios, it's doing what it should when still in closed loop?

If that's the case, a bit more fuel pressure or a bit lower MAP signal might help the closed loop throttle response, no?

edit-- I think I'm agreeing with you, but I'm not sure

That's what I'm thinking.

 

[Muad'Dib]

Well ive done that and it works to an extent.. its like the lesser if two evils.
I can easily increase fuel pressure or even drop in larger injectors to fix the issue... but the flip side is pig pig pig rich WOT AFR's (drop in power). I originally started with 26lb injectors on the stroker.. i dont remember if i had this issue then (probably not) .. but my AFR's were crazy rich at WOT. Dropped the fuel pressure down the best i could to achieve close to optimal WOT AFR's (ran like shit too.. no automization) and did some math to find the now properly sized 23lb'ers.

Im fairly confident that i have this thing dialed in tuning wise given my current set-up. The more i look into it the more i can see megasquirt being the only possible solution.

 

[cruiser54]

Well can't you then reduce the voltage to the MAP to help with WOT?

I thought 24 lb injectors were what we wanted in our strokers. That's what I have for mine although it's still in pieces out in the garage.

 

[Muad'Dib]

Every engine is different. 24lb's is a base line and will usually work for most set-ups. Ive found that in my 4.7 23lb'ers are the right size to tune properly.

RENIX only has two real tuning points. MAP and Fuel. Modifying any of these things will only effect WOT operation. Everything else is controlled by sensors.

Earlier i stated that when i tried higher fuel pressure with lower map to achieve proper AFR's at WOT the RENIX didnt like it as much as doing it the other way around. Lean tip-in was also an issue.

When i had my 26lb'ers in there, i tried adjust MAP voltage lower and lower until i got the AFR's i was looking for at WOT. The problem here was that although it ran great after warming up, on a cold start it wouldnt start at all or start and run like major shit. If i flipped the switch on the MAP (goes back to stock ~5v) and then tried starting again it would fire up. Once warmed up i could turn the engine off and flip the switch back to modified voltage and the it would run fine. Again i dont remember if lean tip-in was an issue at this time.. i was too busy trying to get AFR's tuned. I did also try the reverse were for the most part i left the MAP voltage alone and dropped the fuel pressure down as far as i could. This caused problems also since fuel pressure is needed for proper fuel automization. Imagine just dribbling drops of fuel in there...

So here is the bottom line for me. The only way i have been able to tune my RENIX is by basically tuning on the lean end of the spectrum. I cant tune on the rich end or else im either way too rich at WOT, or operating ability is impacted (which isnt an option on a DD).

Ive been playing this game for a while with my Stroker. Im looking for possible solutions that i can implement on top of my current tune. Something to throw in more fuel at part throttle would be ideal.

 

[cruiser54]

Auxiliary fuel pressure regulator? Corky Bell at Bell Engineering in Texas invented one and he's sharp as a tack on them. Might be worth calling him.

 

[IH392]

Just kinda thinking, would it be possible to change the tps arm so that when you first crack open the throttle that the rate it first moves at, is much higher to compensate for the larger throttle body. Or i would be tempted to put the orginal throttle body back in there. Is there a lot of restrication at full throttle with the old one? Did you ever measure the vacuum at full throttle? I was always curious about this with strokers.

 

[Talyn]

sidewaysstarion mentioned something about accel enrichment that acted like open loop when you tip the throttle in. He mentioned it in respect to the pre 00 OBDII PCM, but maybe there is something similar on the Renix PCM. Maybe it just can't compensate for the large throttle body.

 

[gradon]

Foolin with the AEM this week, I found that I don't want to zero out the fuel trim(for 14.7:1) at idle, or else my cold-start will be too lean. There is a balance with respect to injector size, map voltage, and fuel pressure(if you have the ability to adjust it). A better solution would be a piggy back unit like the SS PSC1/FTC1, Apexi, or AEM that will let you adjust/zero fuel trims in Closed Loop and have full adjustment in Open Loop.

 

[Muad'Dib]

I didnt think that a piggy back existed for a RENIX ECU..

 

[Muad'Dib]

That was a question lol...

I just want to drop more fuel into the engine when coming off of idle at part throttle. I figure something that can interpret the TPS and RPM should be able to do this.

From what i can read, the PSC1 can do this.. but im still unsure on whether or not it will work with a RENIX ECU. Id be willing to do the AEM FIC also if it would work..

Just not looking forward to doing Megasquirt. The "start from scratch" idea scares me.

 

[cruiser54]

That was a question lol...

I just want to drop more fuel into the engine when coming off of idle at part throttle. I figure something that can interpret the TPS and RPM should be able to do this.

From what i can read, the PSC1 can do this.. but im still unsure on whether or not it will work with a RENIX ECU. Id be willing to do the AEM FIC also if it would work..

Just not looking forward to doing Megasquirt. The "start from scratch" idea scares me.

MS would be fun. I'd hate to do all that soldering and assembly of small parts though.

 

[Talyn]

AEM's latest firmware (its beta iirc) has an accel enrichment option, but i have heard it doesn't work well.

 

[Muad'Dib]

Even if i could get something that i could tell ok if TPS volts is between x and y AND OR RPM is below 1200 RPM then make TPS volts = z. Should be simple and do what im looking to do. Again.. i am pretty sure that i can do that with the PSC1 just am unsure if it will work with the RENIX ecu. Does anyone know?

 

[Talyn]

I believe it would possible with any of the MAP style piggy backs. Instead of adjusting the map ad or subtract voltage from the TPS. You of course would want to sample voltage from the TPS on the way back to the PCM before the splice for the adjuster.

 

[Muad'Dib]

Ok guys i need some help!

I have been studying my engine outputs with my newly purchased MT2500. One thing that concearns me is my Short Term Fuel Trim (STFT).
From the research i have been doing, the RENIX STFT ranges in value in closed loop mode from 0-256 with 128 being the median. 128 appears to be the ideal meaning basically that you have as much room as possible to enrichen or lean out the mixture when necessary to do so. If you drop below 128 then this indicates a rich mixture and the computer is pulling fuel to maintain stoich. When above 128, then you are running lean and the computer is having to add fuel to maintain stoich.

My dillema is that according to the MT2500 my Stroker is running rich and the computer is pulling fuel to maintain stoich. My STFT values at idle jump around between 10-15ish to 30-45ish. When using my AFPR if i increase the fuel pressure from stock then the ECU appears to fault and stay in open loop. At this time the MT2500 shows near/at 0 readings for STFT. If i adjust my FPR to decrease the fuel pressure as far as i can go then the STFT values go back up, but not much more than what i see at idle. What this seems to indicate to me is that my Fuel Injectors are too large.

Correct me if im wrong, but in my mind this could potentially cause the lean tip in issues i have been experiencing. If the ECU is pulling fuel to maintain stoich and is running with a STFT value of ~20, then it really only has 20 steps to use (to bottom out at 0) to be able to increase fuel and force AFR's back up to stoich when needed. Is it possible that what im thinking here is true? On the surface when you have too big of injectors you would think that you would have plenty of room to add more fuel when needed, but if the computer does this based on STFT values and is already close to maxed out.. then the computer doesnt really have any more room to add more fuel when needed.

What really has me confused is my current injector choice. As you may or may not know, i started with 26lb injectors that were too large. Now im running brand new 23lb 280155703's. Most Stroker builders use 24# injectors and fare just fine, but for me it appears that even 23# injectors are too large!

Any insight into my post and thinking would be greatly appreciated!
Thanks!

 

[cal]

I dunno, but I'm watching this closely, we run our car way rich..

Sidewaysstarion is getting ready to throw that inline AEM on our car to try and help. I'll let you know how that goes..

 

[Talyn]

What really has me confused is my current injector choice. As you may or may not know, i started with 26lb injectors that were too large. Now im running brand new 23lb 280155703's. Most Stroker builders use 24# injectors and fare just fine, but for me it appears that even 23# injectors are too large!

Do you still have the stock injectors? May want to throw them in there just for testing purposes and see what it does.