Possbile. The flywheel was originally intalled by a shop. Then I removed it to put on the new friction surface and clutch right before the turbo install. Torqued the flywheel bolts to spec. One of the reasons I have suspected the flywheel is because the stumbling occurs righ at the point of engagement of the clutch....but other things happend at that point as well like load on the motor and such.

As far as the MAF on the charged/non-charged side. Wouldn't I want the MAF to read the compressed air and not the intake air??? I am guessing it works either way because the MAF does not read the amount of air but the flow....as in the heating and cooling of the sensor.

As far as the bend, if it was causing stumbling wouldn't I get many other problems as well? The car idles perfect. Pulls through 1st fine, shifts into 2nd and pulls through 2nd with no issues. It is just sometimes the 3rd gear shift and most of the time on the 4th gear shift....all at WOT. I can also get it to stumble sometimes in 4th or 5th gear at low rpm's (2K or less) by pucnhing the throttle real quick. But won't do that consistantly.

If it is the MAF for whatever reason then the voltage reading on my SAFC should be dead give away. My brother had some odd stumlbes in certian spots in his rpm band with his SR20 240 for a long time. He never knew what it was. It was not till one day he happend to notice his MAF voltage reading for the SAFC go funky when these stumbles occured. Put in a new MAF and it cured the stumbling and the whole car ran better. I guess he just had a partially bad MAF.

But if the MAF voltage stays steady and linear when this happens then I would think it is safe to say it is not the MAF.

 

Yeah, you would have to run some sort of bypass system.

im free next monday if you want to swap MAFs and go for a ride.

 

Those who think it might be the bend before the MAF, I can get a 3" piece of straight pipe in there w/o having to redo all the piping. You think that is enough to make a difference?

 

it would be worth a try, but if you had this problem before hand, then it might be because of that.

 

Idea.

My car usually stumbles into 4th, at WOT almost every time, and most of the time at part throttle. This however wasn't happening at the track the other day... I was surprised. It didn't happen a single time. Then I blew the HG. Perhaps it has something to do with fuel delivery, i.e. excessive richness upon the shift or just a drastic change in AF/fuel flow (like when you go from 11.5:1 under WOT to typical no load AF which is like 14.7:1, or at least somewhere near stoichiometric. Since according to the plugs, I was tuned just fine prior to the weekend, and I always got that stumbling, maybe that is the culprit. Then over the weekend I was running lean, and got no stumbling. Perhaps a coincidence, perhaps not.

 

I have the exact same problem(bogging/bucking from 2nd-3rd,3rd-4th) My 96' is N/A. Its not a consistent problem, it comes & goes. This started right after I hade the AASCO motorsports 5lb. flywheel installed. I wish we could get a real diagnosis/solution to this problem cause it pisses me off! Nice #s @ the track!

 

Mike nice times! How do you like those motor mounts? Next time you go to the track, I would like to bring my mustang and see what it runs.

 

My brother had kinda the same type idea. He thinks that maybe my ECU is just not made or likes to see the type of load I am putting down. Going from load to off throttle back to load again could make the ECU kinda freak out for a split second. But all that is just theory....

 

Do you think this hesitation could be caused by your injectors cutting off/out? I forget what fuel setup you have going (A32 MAF and injectors with a 255lph pump right? AFPR and FMU>) Maybe you have maxed out your injector flow at that specific time, causing it to stumble?

Just a thought...

 

not with such low boost.

 

an outsiders 2 cents...

I realy don't think it is the flywheel. It might happen to more people with a fidanza simply because they are more likely to be running bigger hp numbers and pushing their cars harder. Lightened flywheels have a pretty crappy dollar/hp ratio so most likely, if you have a fidanza you have alredy done quite a few other mods.

Hesitation is almost always caused by an excessive rich condition. Your ECU has an "accel" map which is a throttle tip-in enrichment map. Basically, When you go from low TP to high TP very quickly your engine naturally takes a big gulp of air. The accel map tells your injectors to push more fuel to compensate and keep everything within a reasonable afr range. My guess is that your stock accel maps are not tuned properly for higher than stock hp levels... at higher airflow, it adds too much fuel (to stay on the safe side). If I am correct, the good news is it won't hurt anything. The bad news is, I doubt you can get ayone (like JWT) to tune that table. This theory would explain why it happens only in higher gears (more load/airflow) and why it sometimes happens when mashing the pedal when you are already in gear (rapid throttle tip-in).

Just an idea

 

Sounds like the most reasonable suggestion I've heard. It used to happen with my old NA car too. I know myself and Dave B had mentioned it a couple times if I recall. But that still leaves us wondering why it happens to us at just normal throttle positions.

 

Don't know what you mean by "normal throttle positions"....what is normal and what is abnormal?

When it happens to me I am going from very little load or no load to alot at once.

 

I'm saying dave's explanation seems to explain why it happens when you are drag racing, but not when you are just driving down your neighborhood street only using 25% throttle.

 

Wow Mike, congrats on the new PB. Must be fun having to deal with all that power.

Funny you mention the hesitation/stumbling after you shift. After I got my Spec stage II clutch installed and broken in, I noticed that I sometimes get a hesitation for a second when I shift gears, usually at light throttle. Of course, when I try to make it stumble, I can't make it do it. And it doesn't do it when I'm shifting/racing at full throttle. The clutch was the only thing I changed, so it leads me to believe it's the clutch, but after reading some of these explanations it seems like it may by ECU related.

Anyways, good luck getting the car tuned perfectly and improving your times. Soon it will be time to turn up the boost

 

What are your plugs gapped to ? On my SR I used to get heavy bucking right when boost would come on after 3-4 shift, I had my plugs at like 21 thousands and under 22psi it would blow out the plug and cause a missfire and a highly rich condition. I would personally put the car on a wideband 02 sensor, and look at what the A/F is doing in that part of the powerband when its bucking.

BTW I saw you on Aurora Ave n RT59 last week, I was in a silver 04 TL 6MT that I just rebuild the motor in- I spotted the IC from bout half mile away, nice looking sleeper. I work around that area.

 

I actually noticed that car. Turning into that new Naperville motors dealership right? Early in the morning?

My plugs are one step colder gapped to .38 IIRC. At only 5lbs of boost I didn't think spark blow out would be an issue. I used to get this studder when I was NA too, just not very often.

Here is the AFR I am tuned at right now. The red one is the one I went with. Not really pretty but that was the best I could do with an FMU and SAFC. My injectors were maxed out with the blue one using the 8:1 disk so I could not add any fuel.

 

I was going to hard wire my PLX M300 wideband into my Maxima, if you wanna mess around with it on your car lemme know we can do that. Also I noticed that on the RED line your A/F dipps to WAY rich at little lower than 4K RPMs, I know on a 3.0L 1-2 shift puts you in that RPM range, but 3-4 shift should only dip down to around 5K RPM when shifting at redline. It would be interesting to see what the car does when driving it vs just nailing the throttle on the dyno in 4th gear. What fuel pressure are you runing ? What fuel pump ? I would try regapping the plugs to more boost friendly .25, JDM SR20DETs run that gap from the factory vs .40 for the non turbo ones. What kinda plugs do you run ? Highly recomend NGK Copper vs anything else.

I was in the silver TL, telling my boy- check out that Turbo I30- we where out on a Dunkn Donuts coffe run that morning, turning right by Naperville motors- I work next door over at Acura.

 

I couldn't do much with the the really rich spot between 3.5K-4K
fuel management I have. I had the SAFC taking away 18% right in that range and I did not want to correct any more than that.

It is possible that I land back close to 4K rpms on my 3-4 shift since I don't take it to redline in 3rd. With my power curve I am better off to shift at tad over 6K. The only gear I take to redline is 1st. I am making 260whp at aroudn 5K but only 200whp at 6.5K

But I also get the studder if I am in 4th or 5th gear at less than 2K rpm's and stab the throttle, so I don't really know what the culprit is.

I am using NGK coppers of course. I will try a smaller gap and see what happens, I also am planning on adding a straight section of piping before my MAF since I have been told that the curve right before the MAF can cause problems. But if it was the curve in the piping before the MAF I would think I would get much more consistant problems. I never get the studder on my 1-2 shift or once I am in gear, just right when I engage the clutch on the 3-4 shift.