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Topic: too much air? (Read 6712 times) previous topic - next topic

too much air?

The 88sport 5.0 aod, according to my son mason may be getting too much air at wot.
he says that if he floors it, the car seems a little "flat" or lacks response like it should but...... if he backs off the gas pedal about a 1/4'' or so, it pulls much more than at WOT.
dual 2 or 2 1/2'' exhaust with stock headers,
stock fuel pump
explorer upper / lower
larger tb, i think its 70 or 75mm, cant remember but its not stock
stock heads


so im thinking the fuel delivery is not there to match the air flow.

lets see how much i know.........

tps is assisting in signaling EEC to PWM the injectors but the stock injectors are not meeting stoich so he is for general conversations sake, he is running a little lean at wot.
~an adjustable fpr may cure this by allowing a tad bit more fuel in from the rail = inexpensive upgrade
~a little higher velocity fuel pump may cure this as well= little more expensive, offers up the opportunity to do some preventative maint when the tank is dropped.
~swap in an upgrade to injectors which is easy as long as the SO EEC wont reject them
~adjust the trottle cable so that he never feels this again thus reducing his max wot performance and possibly saving his ass:hick:~! too easy

does this symptom sound familiar to those of you who were where mason is today?

thoughts?
 

too much air?

Reply #1 –
Have you checked the fuel filter?  You a fuel pressure gauge that you can install on the schrader valve and have inside the car to see if the FP is dropping at WOT.  I would start here before I did anything else.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

too much air?

Reply #2 –
I dont think a higher volume fuel pump will do anything additional without a adjustable FPR to raise the pressure.  I dont think you should add bigger injectors without a tune to input the change.  Could swap back the stock TB and see if the symptom goes away. 

Is the throttle position sensor in range at WOT?
Mike

too much air?

Reply #3 –
tps is good at wot with an buttstuffog meter.

good points on check the fuel presure,, i feel dumb now but its ok.
when he comes home again ill do that.

i need a fuel pressure extention hose to put it up on the windshield while driving to see whats happening under a load.
i meant to get one of these a while ago.... another excuse to get a tool,, i love it.

too much air?

Reply #4 –
I never had issues when I had a 70mm tb with stock injectors. The fuel filter is a great place to start since it only costs $5.

turbo charged 94 Cobra engine/440cc injectors/megasquirt /5 speed swapped (T5)/maxbox upper intake/70mm PP throttle body/AJE coilovers/2003 Mustang control arms/S.T. sway bars/ES rear control arm bushings/11" brake conversion/manual rack conversion/8.8 TC rear with rear discs and a welded diff/3.73 gears/PLX wideband/199mph speedometer/Aeromotive FPR/CNC hydraulic hand brake/cobra R wheels/....ect.

too much air?

Reply #5 –
Stoich refers to the 14.7:1 ratio at cruse or other light throttle condition... For max power at WOT ratio needs to be around 12.5 for a NA application and around 11.5 when boosted... The extra fuel when boosted is mainly to keep mixture cool to lesson the chance of detonation... At 10PSI my SC Marauder was at 11:1 which is considered a safe tune for those engines...

As suggested if F/P is a steady 39psi at WOT the fuel is at the rail, problem then would be under size injector for your mods...

too much air?

Reply #6 –
say part 2 of your last sentence again,,,

are you saying if i find all is well with fuel delivery, that the injectors are undersized for my minor mods?

too much air?

Reply #7 –
Quote from: jcassity;414995
say part 2 of your last sentence again,,,

are you saying if i find all is well with fuel delivery, that the injectors are undersized for my minor mods?

Basically that's likely the problem... I assume you still have the stock inj and ECM???

too much air?

Reply #8 –
correct,
the reason i wanted a reword is your thinking what i was thinking, needed confirmation

Ill measure the fuel presure first though and swap filters cause i have one,, but Ill take your word for it if the results stay the same.

Mason and i discussed this and i told himi wasnt exactly sure if there is a recommended fuel injector for an SO non-mass, non-ho application where all we did was just increase the amount of air flow.

in theory, i suppose the heads are a bottle neck but those get replaced with GT irons or something better later this summer.
if i can rememdy the issue with the next step up injector and not risk "too much" fuel, keeping the SO eec, that would be nice to know.

too much air?

Reply #9 –
The stock 14 lb/hr units should support in the range of 200 fwhp if everything is in good working order.  If you need to bump it up to 19 lb/hr units then try and find a Mark VII ECU as they are a direct plug in on an SO motor and will support the 19 lb/hr injectors.  At least that is what I have read as I have never done it myself.  Me personally I would just start gathering up the parts for an HO swap and be done with it but that costs $$$.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

too much air?

Reply #10 –
The speed density ecu doesn't know what to do with all the extra air...its that simple.  You have lots of options, but none of them ideal...like the mark 7 ecu will control the 19lb injectors.  But without the better heads and cam you will probably be rich, for the lack of air flow.  You can chip it...$$

I guess I would ask the kid if he is going farther with the mods on the car???  If no, you probably could get a adjustable fuel pressure regulator and gauge....bump it up until the flat spot goes away.  Not to high...like no higher than 45psi.  He may also need a better fuel pump...not sure on this???!!!

How fa$t doe$ he want to go?

Travis

too much air?

Reply #11 –
I dunno about the Mark VII EEC not knowing what to do with the "lack of air" being that speed density still uses O2 sensors and the tables should be able to compensate for that.  The Mark VII's were not all that great at air flow them selves so I think it would be a better situation than what he is in now if in fact larger injectors are needed.

I do agree that the fuel pump needs to be upgraded and an adjustable fuel pressure regulator needs to be installed but again it would only be if the fuel pressure is falling off at WOT.

Darren

83 351W TKO'd T-Bird on the bottle


93 331 Mustang Coupe - 368 rwhp

too much air?

Reply #12 –
By default ford engineers gave there engines lots of fuel...WOT really rich.
The computer has no knowledge of knock...so father Ford made them rich at WOT.
So the average user can add a cone and exhaust to a speed density 5.0HO and it makes more power.
The 88-92 Lincoln mark 7 used speed density, because Ford didn't think anybody was going mod it.
That user is just leaning out the fuel curve....of course that car picks up...a good thing.
But with the SO setup...father Ford...didnt leave much room for mods on that setup.

Travis

too much air?

Reply #13 –
If you plan on making changes to the air/fuel ratio, you should get a wideband monitor. That way you won't be taking stabs in the dark. Its an excellent tuning aid.

turbo charged 94 Cobra engine/440cc injectors/megasquirt /5 speed swapped (T5)/maxbox upper intake/70mm PP throttle body/AJE coilovers/2003 Mustang control arms/S.T. sway bars/ES rear control arm bushings/11" brake conversion/manual rack conversion/8.8 TC rear with rear discs and a welded diff/3.73 gears/PLX wideband/199mph speedometer/Aeromotive FPR/CNC hydraulic hand brake/cobra R wheels/....ect.

too much air?

Reply #14 –
I think your bottleneck is the e6 heads with the explorer intakes and 65mm+ size throttle body.  And like whats been said, I don't think the SO computer and injectors can support your air:fuel ratio.