Back from the Dyno - What next?

[94blackntan]

To make a long story short, my 94 Cobra, which is basically stock with 150K, short of a BBK H Pipe with Cats, and a Flowmaster 2 chamber Catback system. He (my younger brother) also recently rebuilt the T-5, and has a newer clutch. Everything on top of the engine is bone stock. Also, the PCM was bad for 3 of the 4 years he had it, and the mods he did was to compensate for a poorly running car because of the Computer being out. I got it for 82 bucks on Ebay.... much better, but still underpowered.

I changed the plugs, air filter, put on a set of Ford Racing plugwires, and took it to the DYNO..

It was running like pure crap, and they tuned it for me.

First pull - 185 HP / 210 TQ

The AF Ratio was well over 15, and as high as 16.5 on the high end of the power band, and the mechanic checked the Stock Mass Air meter, and the with my bro having a K&N for 3 years and not cleaning it, it was BLACK.

He put adjusted the air box (wasnt quite clamped down right), and cleaned the Mass Air Meter and power jumped on the second dyno run

Second pull - 218.5 HP / 245 TQ

This pull got the AF ratio down to about 15, throughout the entire power band.
For the final pull, replaced the Fuel filter which was probable original or close to it, and set the timing to 14 degrees, as he had it around 0 degrees.

Third pull - 223 HP / 251 TQ.

AF stayed around 15, and it's still running lean, but more like 14.5 throughout.

He said I should run it for awhile for the computer to get used to the Mass air meter being clean, and I actually disconnected it to let it learn again, as it ran forever in a horrible state.

My question has 2 parts. Will a new 255 LPH fuel pump and a fuel pressure regulator get the ratio down to where I need it to make more power, and most importantly....

Is there anything I can do to the engine to get a noticeable increase in HP?
With a good clutch, tranny, and 3.55s in a recently rebuilt rear, I'm not worried about the power. I just dont want to spend money on parts I won't be able to reuse when I go to rebuild the motor (probably a DSS / Kenne Bell combo, unless something better comes along).

I am trying to keep up with a buddy of mine who is at 300 rwhp on the dyno in a 92 limited edition convertible.

Recommendations?

THANKS in Advance.

 

[Mac-man]

the regulator will probably help u moreso than the pump in your current state of form. the pump wouldnt hurt, but probably also will not help unless ur pump is already going bad. the regulator will allow u to introduce more fuel into the engine thus richening it up some. as for as mods for power, have u dont any kind of headers and midpipe? what about pullies or a cold air induction? u could possibly throw in a slightly more aggressive cam and pick up some power there since ur car already has gt-40 heads and cobra intake. u might also want to think about changing to a different set of cylinder heads.

 

[96darkhorse]

damn , you should be making more power than that! that tq number is real low!

 

[94blackntan]

You were right.... I went and got the Dynosheet, and I was off slightly.

Torque was 263.9.

Slightly better, but not much.....

What gains can I get without going too deep in the engine? I was considering
going with AFR185 heads on the next engine, and the stock headers are on the car.

But if I get heads, I'll probably do the cam, and tons of other parts while in the process, and I'm trying to stay on the relative cheap until I redo the whole thing.

Any ideas? and no... no pulleys, CAI, TB, nothing is done on it... Period, but I want to know the way to best gain HP/TQ.

BTW, here's a pic...

 

[Mac-man]

i could see u seeing somewhere near 300 rwhp (possibly) with a pretty aggressive cam, and those heads with the supporting mods such as headers, and whatnot. i would do some type of shorty style header at the minimum. i bought some bbk's for my 94, but since it got hit yesterday i kind of got other issues to work out so now i am going to have to sell them

 

[mytight95]

so your car is a Cobra, or a GT.

If it is a cobra you are really really down on power somewhere. I understand the lean thing, i fought mine for 2 years..... more mods i done the leaner it got.... get a custom chip with dyno time, and you will get everything where it needs to be. If the pump is on its way out it will make it run lean by not supplying enough fuel pressure. Get a reg. and a gauge, when you shut the car off watch the gauge to see if it holds pressure. Another thing you can do is to check with the engine running to see what the most PSI you can get out of your pump is........





jason

 

[95WhiteVenom]

#'s aren't all that bad. Your car is similar to mine. I haven't dynoed mine yet but those numbers could be a lil better. A rebuild would be a good idea but might as well do the heads and cam too at the same time.
I'd love to put mine on a dyno just don't think it would be worth it till more mods. come.

 

[Grn92LX]

The regulator and pump will not help. I would try disconnecting the battery over night to erase the KAM (keep alive memory) and then the next day put the battery back and go for a drive and a WOT drive and hope the eec can get the fuel curves good.

If not, maybe you have a vacuum leak or you need a tuning device. I would not do a chip.

 

[dstanggt50]

I would just get the regulator so you can play w/fuel pressure, maybe jacking it up a little will get you to run a little richer. I always thought those cobras stock dyno'd around 230-250rwhp
Other than that I would chk for vacuum leaks, codes, maybe throw on a different maf. (Mine was crapping out on me w/no codes, but my voltage @ idle was around .5, replaced, the last time I chk was around .8 or so, runs a lot better.)

 

[mytight95]

why would a regulator and pump not help if he is not getting adequate fuel pressure.......????

That makes no sense


jason

 

[final5-0]

I don't think your too far from about right with those numbers considering the milage and history of how the car was maintained.

I know for sure a boost in fuel pressure at the dyno session will drive your ratio down somewhat but for how long I could not say due to the pcm trying to make things normal again.

I think I would want to do a compression test and or leak down test to see how effectively the rings are sealing the charge in the hole.

You most likely will not match your friends numbers with the miles on your motor and just a few mods like pulleys and the like.

If you do indeed have plans like you talk about then you are wise not to put your money in things like 19lb called mafs or any other items that would be too small for your long term plans.

Later
Grady

 

[mytight95]

Grady, if you raise the fule pressure manually the computer will regulate that as well, even if it is running lean still..... I know you know what you are talking about so i am asking a genuine question not an assenine one. If you don't mind explain that a little better.




jason

 

[final5-0]

Grady, if you raise the fule pressure manually the computer will regulate that as well, even if it is running lean still..... I know you know what you are talking about so i am asking a genuine question not an assenine one. If you don't mind explain that a little better.




jason

Jason

This can be a touchy subject to talk about and I've seen threads on other forums get quite heated about this so I'm only gonna talk in general terms. I really don't think we'll have that kind of prob on this site but anyway.

Basic Operation

In a perfect world of everything being just right on a stock Stang the pcm is trying to keep things at at the same ratio at all times. As sensors and the like get old the pcm can use its adaptive strategy to make adjustments to compensate. There is a range or amount of adjustment for that strategy.

AFPR Operation

Say you change the pressure by a small amount which in turn changes the ratio. The pcm will see the change and will try to compensate. I know this to be true.

I've seen the pressure raised at the dyno and on the nest pull you see the lower ratio and gain more power.

Here are things to consider

Here is the thing to think about the above sentence. After say a week, what has the adaptive done? Has it voided the gain? There has been evidence to show that has indeed happened.

I myself have never owned an afpr due to the reason that I've always tuned by manipulating the pcm values. When you use that method of tuning, moving the fuel pressure will be counter productive to your pcm changes.

I've seen some say that you just keep upping the pressure until the pcm has reached its adaptive limit and all is well. Maybe, maybe not! I can't say for sure but my common sense tells me this about that example.

Most of the peeps who say those things don't have a wide band so they have no way to know for sure what their ratio is after the dyno session and it is my gut feeling that things don't stay the same over time.

Before I end this post I wanna make it clear ...... I have no hard data to support my thoughts about the above sentence.

Later
Grady

 

[94blackntan]

Thanks alot!!!

These Cobras came with 240HP from the factory, at the flywheel.

I did what someone suggested, and disconnected the battery.

Maybe the PCM will self correct, reset the tables, and richen up.

Otherwise, I guess there arent too many options. The shop suggested
a CAI, but of course he was going to sell it to me. I could do that, an AFPR,
a new fuel pump, and still be lean and only gain a few HP.

What rear ends do you guys with high HP rebuilds use?
I was thinking about steepening the gears to 4:10s, but would want to rebuild or replace the rear end when doing it, so I could reuse it in the new application...

 

[94blackntan]

Actually, now that I think about it, If I were to get a chip (Diablo),
would It be able to fix the lean condition? I could always get it
reburned later, or isn't this worth it for an unmodified car?

 

[mytight95]

good info....

94blacktan.... i don't know if you would like the 4.10's with the cobras steeper first gear.... I know i am changing mine out, this is a personal preference however, and i only said that so you could think about it........

cobra t5 1st gear 3.35
plus a 4.10 in the rear =very little first gear....just my .02... I am also upgrading the rear at the moment, the most positive feedback from everyone so far has been a detroit locker rear......but i was looking at the detroit tru-trac setup.....



jason

 

[94blackntan]

The car has a rebuilt tranny, and I doubt my brother swapped for a Cobra T5. I really wish he had kept the original tranny for the car.

How much for the rear axle replacement?

 

[mytight95]

i was thinking the car was a cobra based on the pics.........so the power level does seem about right......

unsure on the axle replacement good axles seem to be around 250$ for just parts...



jason

 

[mo_dingo]

Yep, your O2 sensors will indicate a rich condition and trim fuel injector pulse width to compensate. So it's truly pointless to get an AFPR unless you are running high flow injectors and need the extra fuel pressure for proper fuel dispersion.

You will only see temporary changes in a/f ratio from the AFPR, so forget it.

But when the guy cleaned the MAF sensor, how did he clean it? Did he remove it from the housing or did he just spray some carb cleaner in the sample tube.

If he didn't remove it, you need to. That sensor is very very sensitive to debris.

Disconnect your battery, first. Remove the 2 T-20 saftey torx screws, carefully slide the sensor out, and get it on a bench. If some obvious debris is still present, you should spray it with carb cleaner to get the excess off. Once it's clean, take a q-tip and dip it in carb cleaner, and carefully clean both thermistors. Then reinstall the sensor to the housing.

Seeing the condition of your MAF sensor, it might need to be replaced because of neglect. But you need to remove your IAT sensor as well, and clean the hell out of it. Make sure you reinstall it the same way it was. It has a plastic u- shaped piece that surrounds the element on the IAT. The plastic U needs to be perpendicular to the air flow, so the air flow will hit the red element without obstruction.

After you clean both of those, you need to test the ECT sensor also. The sensor's resistance will decrease when temperature increases, thus the voltage drop will decrease as well. The control module will put out a VREF of 5V. So you should see somewhere around 3V when the motor is cold, and around 1V when the motor reaches operating temperature. I don't know the exact figures, because I my book only outlines MAF & IAT voltages as a function of air flow and temperature, respectively. Someone else might be privy to that info so hopefully they will post it.

The MAF/IAT/ECT sensors are the primary controls for air/fuel ratio when you are at wide open throttle or 1st 20-120 seconds of startup. Either of these sensors will have a drastic effect on your a/f ratio if they are dirty or out of operation specs.

Let us know what you find out.
Scott