axr6

Well, OK, no car is EVER too fast but, this one seems too fast for the modifications it has. Here is the short version.

I started out with a reman engine, stock twins, M2 intake, M2 SMIC, PFC, DP, STOCK CAT, straight 3" pipe for exhaust and a AEM Wideband. On install the PFC boost was set on base settings(56 Pri, 64 Sec), supposedly good for about 10 psi of boost. Well, right out of the gate I got 13.5 boost and had to lower the settings quite a bit to get it back to 10 psi.

Next strange thing was my fuel situation. The injector map my mechanic gave me was "supposed to be" quite rich for my mods. Well, the AFR went lean, about 12.6. above 6000 RPM with 10-12 psi boost. Finally I had to max out the PFC fuel inj. map settings at high RPMs to get me to 11.2 AFR near redline at 10-12 psi. That with the stock cat still on.

So... I just finished my metallic cat building project and installed it on the car, together with a Corksport cat back. Result: the car gained tons of power and now the boost is running absolutely wild. With the boost settings that I had before for 10 psi, now I saw 13+ immediately. So, I got my Pri boost set down to 36, sec to 44 but to no avail. The boost snaps instantaneously now and first goes to about 10 then suddenly swings higher where I hit the PFC fuel cut a couple of times. I am not sure it it is called "boost spike" or "boost creep" but, I picture "boost creep" as a slow building of extra boost. This one just spikes, right now!

With the stock cat at 10 psi my injector duty was 91%. At 12 psi it was 95%. Now with the metallic cat installed my injector max readings are up to 99.5%. Interestingly the AFR seem to be OK, still low 11s and even saw some 10s.

What is going on here? As much as I've read this forum, my mods do not seem to justify those high injector duties, nor the boost spikes, or creep even with a metallic cat converter. The car is pretty wild now but, the boost needs to be controlled. Is porting the WG the only solution for me? Would I also have to step up to larger secondary injectors to reduce the high duty cycles? It seems that the stock injectors should support this much mods at relatively low levels of boost....?

Thanks for any advice.

Albert

Brent Dalton

iTrader: (31)

You need a boost controller besides the PFC such as a Profec B. Also porting the wastegate on the turbo's should totally clear up the problem if the boost controller does not.

Narfle

iTrader: (16)

That SMIC is where its at. Most people will stay with the stock intercooler til they bust it and its a big ole bottle neck. Im not as fast as you but I will tell you I dont like to floor my car. 1st and 2nd gear are more about prayer than steering.

Porting your wastegate should mitigate or perhaps nullify your overboost. Getting larger injectors will bring those duty cycles down. You can go with 1300cc injectors in the stock rail or upgrade pretty much everything and get 1600cc injectors that arent as prone to breaking. Now many people have had lifelong success with the 1300cc overbored stock injectors. But some have not. Hope this helps.

And like memphis said. The pfc isnt the best at boost contro. I guess its got other stuff to worry about. The profec B is uber-functional(I hear better things about the spec 1 than spec 2 but you gotta find it used). The blitz SBC i-color is uber bling(nearing a thou so it better work)

jic

iTrader: (1)

Herblenny

iTrader: (13)

1. I thought AEM only went down to 11??
2. where did you mount the O2 sensor?
3. did you run your car with stock pfc map and see what your a/f readings were?

I would get your wastegate ported.. thats not a bad idea... but alot of work!

Just to be safe, I recommend you getting a pop off valve. Its an easy engine saver due to boost spikes.

Also check all your rubber lines. Make sure none has any rip. especially to the ones to your wastegate.

axr6

The AEM supposed to read only down to 11 but, I have seen many reads in the 10s on its digital display. I mounted the O2 fitting about 3 inches into the midpipe, before the Metallic cat.

I think that the fuel map that I got with my installation was very near base and my ARF reads were 12.6 at 10-12 psi boost, above 6000 RPM. Below that RPM they were in the low 11s. So, it was going lean as the RPM increased.

At this time I do not suspect any torn lines as the boost pattern was perfect and rock steady as of a couple of days ago with the DP, Stock Cat, Straight Pipe cat back combo. It went wild after replacing the Stock Cat with my homebuild Met Cat. BTW, I made the cat out of a E-Bay SS midpipe and a standard 300 cell per square inch Metallic cat core, using an airpipe for the smog pump. Looks almost like this cat flows much like a straight mid pipe, causing all these boost problems.

Still find it hard to explain those high injector duty cycles and the need to max out the PFC injector map. I've read that the stock injectors/fuel system should support 420 flywheel hp at 100% duty cycle and I do not think that I am even close to that power level. Yet, I am showing a peak of 99.5% (with the boost spiking to about 13 psi)

I know about the work for porting, I'd hate to take the turbo off again. Installed it a couple of months back with the new engine. Wonder if a Profec would get it under control? Or, I may need some backpressure. Way back with my first FD when all these electronics were not available, I controlled the boost spikes from the midpipe with racing Supertrapps, just adding or taking off plates. That was a pain!!! The pop-off valve sounds like a good idea. Thanks.

ROTARYFDTT

iTrader: (4)

Normally I wouldn't do this and post off-topic, but are you serious?

Larz

Damon used a manual boost contoller with success. They're cheaper, too. I think he has an install write up in the archives.

axr6

Trying the manual boost control would be a good idea to see if the boost is controllable without the porting of the WG. I'll do that first.

Still wondering if, given my original mods of intake, IC, DP, Stock Cat and cat back, were my maxed out fuel settings on the PFC injector map anywhere near justified? I had to use 1.496 max values in rows 16 and 17 at high RPMs to get me to 11.2 AFR. Anyone else had to max out like that with only 10-12 psi boost?

DaveW

I'm sure you know this, but ball/spring MBC's are better than needle-valve MBC types which still rely on the stock solenoids for control.

Narfle

iTrader: (16)

i like a lot of space when i do it. its expensive in gas. its risky if my rear end breaks loose. its risky if my engine blows. im not a little kid anymore. i dont need to floor my car to love it. and yeah i love to floor my car i simply dont like to. ie: its fun but its against my better judgement. the situations in my driving career where its been anything resembling rational to run a mid 12 second 1/4 mile(estimated) on public roads have been few and far between.

Cgotto6

iTrader: (8)

You shouldnt need to port your wastegate. Thats the fix for boost creep. Sounds like you just need to get a boost controller of some sort, let it be electronic or mechanical.

Joe Geiman

At 90% duty you begin to lose fuel control. Upgrade with a higher flow injector.
With an adjustable fuel pressure regulator, you could raise the fuel pressure but then the low speed fueling becomes sloppy. For drag racing, for short runs at full throttle, raising the fuel pressure works pretty well if the injectors go static, or 100% duty. You can always change the fuel pressure back when you are done.

Joe Geiman
Gasoline Alley Fuel Injection
4-D Gasoline Alley
Indianapolis, IN 46222
www. lindertech.com

axr6

Thank everyone for the advice and help.

Looks like it is boost creep, after all, even with the met. high flow cat.

Today, I took out the pill from the wastegate control line and were hoping to get a base 7 psi boost. Instead, it started at 7 and by 7000 RPM it was up to 12.5 psi boost. So, looks like back to the stock cat for now. I have a few questions left.

1) When I take the pill out, should the boost drop to the base spring pressure, despite the PFC being in the circuit?. Will the PFC not try to control the boost still?

2) If I return to my Stock Cat for now, will I have to reinstall the pill or would the PFC take control without the pill?

Thanks

Albert

dgeesaman

iTrader: (7)

That's what I would have expected. The pill is a boost control component, and boost creep is not solved by a boost control. Boost creep is only solved by increasing wastegate port size (or adding restriction).

Yes. The PFC and pill work together.

Put the pill back in and tune it using the PFC.

Dave

ROTARYFDTT

iTrader: (4)

Not even going to bother with any further comments. But I am sorry if you worry about popping your motor everytime get into it.

axr6

Thanks Dave

Since I really do not want to take off my turbo now for porting, it is back to the stock cat and the pill. Car is plenty fast for a retired racer, even with the cat...

Or....

I could always do what I used to with my first FD (with MP) to cotrol the boost creep. Install a set of Supertrapp plates. Hmmm... have to think about it.

I suspected too that it was a boost creep but, were hoping.... thus the test to remove the pill.

Cgotto6

iTrader: (8)

Do you know the differences between boost creep and boost spikes?

Spikes are caused by the turbo control system not being able to react fast enough to keep the boost to the desired pressure.

Creep is when the boost control system is overloaded by the amount of volume, so it has no choice to keep increasing the pressure.

It sounds like you have creep, so a boost controller should fix your problem. That is unless you are experiencing both creep and spikes.

If you are getting both, and you dont want to take everything off (turbo wise), i like what ive been doin for the past year. I just took my stock cat, and hallowed it out. It keeps boost in check real well, looks stock, its not too loud, and its cheap as hell.

Edit: Uhh, I just read your initial post again and I read this..."I started out with a reman engine, stock twins, M2 intake, M2 SMIC, PFC, DP, STOCK CAT, straight 3" pipe for exhaust and a AEM Wideband"

You say you have a straight 3" pipe for exhaust. Does that mean your not running a muffler at all? Just a 3" pipe for your catback? Cause it would definetly help you to put a muffler on there to try to keep the boost under control. and damn, isnt it loud?

You probably meant 3" piping to a muffler, but you never know...

axr6

In my post I went on to explain that I did install a Corksport catback when I removed the stock cat and put in the metallic cat. Of couse the Corksport is a 3" ID straight through canister so, it will not help with the back pressure. Maybe something like the dual tip RB might provide enough back pressure.

I DID RUN a 3" straight pipe with the stock cat. That combo worked well and was not too loud for my liking. The stock twins, stock cat combo provides a fair amount of muffling. The straight pipe and I go a long way back when in 1994-95 I tested several cat backs in real world test, by doing repeated acceleration tests from 60 - 160 MPH. The straight pipe was unbeatable, particularly showed well above 130 MPH.

Yes, I think that I know the difference between spikes and creep. This one is boost creep. With the pill out, it gradually kept rising to 12.5 psi, when I finally decided to shut it down. Unless I am wrong on this issue, a boost controller would not fix this problem.