Great power at all throttle and rpm but at wide open.It runs great but at wot it stalls bad.No codes, great cold start and idle.All the stats are good but the o2 is reading at wot is in the 800mv + range.

 

The stock O2 reading is not a good indicator for WOT.

What are the engine, fuel system specs? Falling flat at WOT is most likely lean.

 

The motor is a 400 sbc,30lb injectors,ported plunum,l98 cam,tb bypass,air intake sensor relocated,flowmaster exhuast.The vitals are perfect all the time,mas not maxing no codes fuel 42psi.I did'nt put on an afpr on it yet because I thought the 30 lb squirters would be enough.How can I tell its running lean?The prom seems like a perfect match.So I tend to think its not the programing in the prom.

 

Lets say the stock 305 chip and injectors proved enough fuel for 230hp (92 305). Moving from 19lbs/hr injectors to 30lbs/hr units is a 57% increase in fuel, all other things equal. Thats enough fuel for 360hp with the stock prom.

The first test I'd do is raise FP and see if WOT performance increases. If you run faster, you are lean. Check FP at WOT to make sure FP isn't dropping.

Really you should start rich and tune towards leaner. Start with FP way up(assuming the pump can keep up) and reduce as performance increases.

 

Brent's correct; that your displacement has increased just under 33% while your fuel has delivery has increased 57% (possibly more if those are SVO injectors which would act more like 33#, using the method GM rates their injectors vs Ford).

Also, you give absolutely NO DETAILS about your engine. Cam, heads, intake? So it is difficult to determine what your flow requirements are.

Brent is also correct that you should not rely on the stock O2 sensor for fuel requirements. But, IF it were accurate, it would suggest you are lean, as Brent mentions.

I don't necessarily agree with compensating with FP alone. FP does not increase fuel delivery linear.

 

Agreed, raising fuel pressure certainly isn't the best way to handle WOT fueling. I would think it is a decent way to get a *quick* bearing on where you are at fueling wise as long as the fuel pump can maintain the pressure.

 

Stock 400 74cc heads,l98 cam,ported plunum,flat top pistons.I don't understand the dicplacement and fuel delivery point.If the cid is 33% increased and fuel delivery 58% would'nt you be saying I'm running rich?The fuel delivery 57%would exceed the dicplacement 33#.I will check for pressure drops though.Do you think my ac delco fuel pump will live at 50psi?

 

The motor runs perfect at all speeds and rpms.But running lean would make it fall on its face?

 

Formula, that is EXACTLY what we are saying (your fuel exceeds your displacement)...but there is more to it than just that, that is why you also have to look at what the mods are...which in your case appear fairly mild for a 400.

However, IF your O2 sensor COULD be relied upon, 800 mV is actually a little low.

Only a WB O2 sensor is accurate though. The 800 mV is kind of meaningless and it could actually be much different.

[This message has been edited by Glenn91L98GTA (edited August 30, 2001).]

 

Maybe I should have worded that better.The car runs perfect and I think reprogramming the prom isnt the answer.Thats why turning up the fp sounds right.The motor will run its **** off 1/2 3/4 9/10 throttle.Just that 1/10th couldnt be the prom,yes no.Considering the fp is fixed at wot,that does seem to be the problem.The fuel pressure was lower the first year of tpi.What about my ac pump at 50 psi?

 

Then this has nothing to do with Eprom Burning. I suggest that you ask the question on the Tech General or the TPI Boards then.

So before I lock this thread as this is DIY PROM Burning (Vader gets angry when we answer his Tech questions), just remember that when you are in Closed Loop, the ECM will make corrections based on the O2 sensor (which is why part throttle feels fine). At WOT, the ECM ceases to correct based on O2 sensor. This is when you see ALL the problems with the eprom as now you rely on the accuracy of the calibration within the eprom. Which is why you are experiening the problems that you are.

You are trying to come up with a "mechanical correction" for WOT which says your Eprom is not right.

Why do you think GM has a different eprom for a 350 and a 305?

[This message has been edited by Glenn91L98GTA (edited August 30, 2001).]

 

ultimatly the prom will need need burned but I did'nt think the tpi board could answer if the pressure raised would help for now(or that would indicated a need for prom ajustment).

 

I really hope help on this board does'nt end up in "there is a reason for 305 & 350 eproms,duh".It just semmed a little harsh

 

Besides there is no production 6.6l eproms.So if I want to find what needs changed in the eprom,I can use my mechanical trick to help.

 

SD (which you have) calculates the amount of time to keep the Injector Pulse Width based on a number of parameters in the eprom. One is Displacement and the other is the size of the Injector.

The 350 has a different displacement and injector size than a 305 and (guess what) so does their eproms.

Has the light clicked on yet?

 

has the light clicked on for you ???in 85 there was no sd tpi.Mine has a mass airflow sensor,heard of one?

 

That is why guys with "stroker motors" need to get a new eprom.

Do as you wish, but you will not perform as you ought to. All these "mechanical methods" arose in the 1980s because no one knew how to burn an eprom (except a few techies that made big bucks...and then they generally didn't do a very good job as they didn't know what we know today).

This is the primary reason so many guys that should perform a LOT better based on their mods are so slow. And then they want to know "what's wrong with my motor" when a Mustang beats them. Maybe that is why Mustangs were so much quicker than F-bodies back then?

But I am here to talk about eprom burning, as I said Vader gets mad at me when I start stepping on his turf and I get a nasty e-mail from the Admins saying "you should have locked that thread". Right now, you are not talking eprom burning and technically I SHOULD be locking this thread.

 

My mistake, I thought you were the guy with the 92 (I've been answering a TON of questions).

Well, guess what, you have even a bigger problem. MAF maxes at 255 and you don't even have eprom calibration then, now you are running on luck.

Good luck and see you on the Tech General Board.