feels stronger at 3/4 throttle

[4-71/Z-28]

First off i do not have a scan-tool yet, i was just wondering if this has happend to someone else that could give some advice. My 87 GN runs fine, but it runs a little stronger at about 3/4 throttle than full throttle. The only thing i have done are K&N filter,thrasher street chip, hooker exhaust(no cat), 3" downpipe. Has this happend to any of you? By the way, THANK GOD the site is up again ive been going insane for the last week!!! :hail:

[Keller]

THANK GOD the site is up again ive been going insane for the last week!!! :hail:

You? What about the idiot that's been trying to get it up and back on the net? :ow: :yawn:

Without a scan tool, you just don't know some of the answers. It may be knocking at full throttle. That could lead to ignition retard, or boost being pulled out in extreme cases. And/or, you may have inadequate fuel delivery. That would cause the above. You need the tools to tell the story. In really bad conditions, you could blow a head gasket from the car leaning out badly.

Didn't Turbo Claus bring you a scan tool, boost gauge, or at least an audible knock warning for your favorite winter holiday? If not, why not take the plunge?

[PaCemkr86]

do you have a boost gauge?

[4-71/Z-28]

i dont have a mechanical boost gauge in it, but i plan on borrowing one from my mustang this afternoon, i will let you know how much its boosting

[buddiiee]

quick question, for the masters on the site. if hes done his air filter, and turbo back exhaust, but kept the maf and fuel pump stock, wont he be maxin past his maf bigtime, and lean out regardless? how common is that? i think thats whats goin on in his car.

[Keller]

You make a good point: All the mods are "airflow" mods. No "fuel" mods are mentioned. The car may just be running "dry" at WOT and full speed.

This is where scan tools, FP guages, etc. really help.

Not sure I understand the 'maxing the MAF' comment. They can handle a lot of boost and HP just fine.

[buddiiee]

when one 'maxes their mafs' their turbos draw more than 255 gr/sec worth of air.... so now, theres more air physically flowing in, than the car was set up to meter. so now (for ex.) theres 270 gr/sec of airflow at wot, but ya only get 255 gr/sec worth of fuel, and bam, unbalance. which is what my car did.

[PaCemkr86]

when the pcm see's the maf @ 255 it has PEM
Power
Enrichment
Mode

[JHensberry]

I asked a similiar MAF question while back and got the response that the chip makers have a solution for fuel control when the stock MAF maxes at 255. And all the new chips that will go beyond 255 measure it in 20gps increments instead of 10 like the stock for example. As far as the current thread, hard to say what is going on with no scan tool data.

[buddiiee]

So, there's solutions built in for airflow past 255 from the factory, AND from modern chips? Then what's all the fuss about the LS1 MAFs and translators then? If the answer is "Well I get better flow that way." then that doesn't make any sense, 'cuz you were already getting more than 255 gr/sec. worth of air anyhow, so flow is obviously not a concern. I don't get it. Please explain.

[JSAautomotive]

Understanding that these systems are archaic in the fact that the fuel cells in the ECM are limited to what the MAF tells it to do, and which fuel cells to apply correspondingly. 255 gps is all the ecm can see and all the fueling that the factory ecm can provide. Not unless you want to rescale the MAF cells in the ECM vs the MAF output of the MAF, then you've got something. The only thing that I know of that can do that effectively will be that new Pro MAFT product. After talking with one of the head designers of the product, I can see how this would be the poor mans fix-all next to going to some full blown stand alone ECM or a piggy back system.

As several have mentioned here. You need the basics to start with 1st. You need to know exactly where you stand as far as air/fuel ratio. Watching the knock sensor via a scan tool would be another valuble input. A dirty/easy way to see if you running lean? If you have an adjustable fuel pressure regulator, add 10-20 psi to your fuel pressure and see if you get the power back up at WOT or just pull a plug and see how white the ceramics are.

[buddiiee]

i see. will do.

[kenmosher]

A couple points ...

When the magic 255 is reached, the strategy has been to increase the PE and AE trim numbers to keep adding fuel until the injectors go static. There are variatiions of this scheme, and despite the crudeness, it seems to work pretty decent.

All of Bailey's extender chips rescale the MAF tables to the MAF output (not just the MAFT Pro), so he effecitively "extends" the table and with a MAF that can physically measure more airflow (like an LT1 or LS1), continues direct feedforward correction of fueling.

Reading plugs is really difficult in these cars ... you need to pull the plug immediately after a WOT run, since the lean cruise strategies will whiten the plug almost immediately.

[buddiiee]

i see. i know what i have to do now. totally. i just have to keep on testing and tuning. im going to throw some numbers at you here soon, so you can tell me what theyre supposed to be at. thanx.

[JSAautomotive]

Totally agree with you Ken.

Since driveability is what I do for a living, I see alot of these cars day in and day out. Not just GM products, but all makes and models. Most of the "chips" out there are mostly hit or miss. Some better than others. There is usually at least one driveability complaint I see with nearly all chip manufacturers. Coming from working with DFI systems since John Meany ran the company, I've always been a big fan of having full and permanant control of the system.

I undestand your "effective" fuel tables comment, because you can't add more fuel cells to the processor. The spectrum of the Block learn cells are limited by the processor. The more block cells you have, the more accurate you can be in hitting the A/F ratio based on RPM, load, or specific conditions. The Buicks are archaic in that manner as compared to say a Motec unit. And this is where some of the problem lies in having the performance along with factory type driveability.

Not familiar with what Baileys does, I'm assuming they do exactly what you say. But then you probably can't control timing or boost via just the chip and MAF installation. The nice thing about the Maft Pro is that you throw away the MAF and you can control timing and boost via the solenoid. I saw that in iteself as a big plus. Not to mention you can wire in your wide band O2 into the system and bascially dial up an A/F ratio and the system scales itself to hold that A/F ratio. I'm going to buy one and try it out.

[Ormand]

He may have hit the limit of the MAF, at 255gm/sec, but not likely if there are no fuel mods on the car. Once you hit the 255, you can still make more power, but it's just control of the A/F is not as accurate, since the ECM has to "guess" at the air flow.

[mikeelia]

Well, I've noticed the same thing on my car. Not at WOT or even pushing it, but when just "going easy": It seems a little "flat" [maybe even a little stutter] at first, and if I push it just a bit more it takes right off...

In my case, I have a feeling that my gas might have gone bad though, since the cars been sitting for a few months since I drove it last. I usually try to put some better gas in when it is going sit like that [invest in a little 100 octane stuff] but I don't think I did that the last time.

I know, I know, I should drive her more, but she's the garage queen now and my new Mustang is on the road collecting the dings and scratches [and miles!]...

Mike E