eec shuts off above 7k rpm?!?!

8URVETTE · Feb 16, 2006

So the title says it all. Everytime I spin the car up into the 7k range the car basically just shuts off. Its like someone just turned the key off. I've been told by many that a stock a9p computer just cant keep up at these rpms. I'm wondering if anyone would know if a pms (in stand alone) would cure a problem like this? How high up (rpm wise) will a pms in stand alone go? If you've ever had this issue please help me out with some tips.

HISSIN50 · Feb 16, 2006

It sounds like you are hitting the stock rev limiter (6250 RPM). If you use the stock tach, they tend to read off (generally high) by a percentage, and at 6-7K, that percentage yeieds a noticable number of RPM's off.

A stock motor has long since run out of air at those kind of numbers, and if you have supporting mods to spin that high, chances are you have a tune in place, which can delete the stock rev limiter.

Good luck.

5.0 Nostalgia · Feb 16, 2006

Do you have any addition information about your combo? If your can is stock, it's not supposed to rev that high. If you are reading off an accurate tach, then you have someone bypassed the limiter as hissin noted.

Black1987Stang · Feb 17, 2006

7k??? damn thats high....like hissin said, if it really is 7k the rev limiter was bypassed. And make a sig so we can see what you have done....Stock valve springs dont like to work well at high rpms, i would think the piston would have met the valves by then

8URVETTE · Feb 17, 2006

Sorry, I should have listed the combo. Its a 306 with apporx 13:1 compression. Ported tfs heads, n-91 cam, victor intake, 90mm tb, 4.56 gears, etc... It made peak power at just a tick under 7k. I had a sct chip last year that bacically just set the rev limiter up to 8500 and turned the egr off. The car runs great but if I ever try to really shift it hard, blurp the throttle (traction reasons), or even just rev it slowly up past 7000 it just goes wacky. Ive heard that there is a company that can put a crystal in the processor that helps this problem but Id like to know if the pms would work just as well? If it cant do standalone up that high I'll have to look to a different route. thanks!

jrichker · Feb 17, 2006

The likelyhood is that you either have an ignition or fuel delivery problem.

The computer will run fast enough to keep up with any RPMs the engine can turn. The 15 MHZ clock gives an 1 microsecond average instruction cycle time. The computer can process instructions 100 times faster than the engine can run, if the engine could turn 10,000 RPM.

Dump the codes and see what the computer says is wrong…

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.

8URVETTE · Feb 18, 2006

We've tried that, no codes stored. Fuel delivery isnt an issue. 255 intake with a t-rex. Fuel pressure stays the same throught this whole ordeal. Any pms users out there? Whats the rpm range of the standalone feature?

vristang · Feb 18, 2006

Yeah, fuel should be good, unless you have some weak injectors. What size are they?

13:1 CR!?! What kinda fuel are you running? Diesel?
That CR combined with 7k rpm will throw off all the estimates for fuel and timing needs that apply to the typical 5.0.
For example you may have to bump the fuel pressure, so that the injector duty cycle is appropriate for 7k. Most likely this will cause some drivability issues at low rpm, so be ready to complain about that next. If you were at 90% duty cycle at 6k (and this would be reasonable for most street 5.0s), then by 7k the injectors will be fully saturated, and not be able to keep up. You may need to "Supersize" standard fuel injector size estimates.

Yeah, you probably need a tuning unit of some kind, simply due to the CR and top rpm. Most here will agree that mail order chips are trash.

The EEC-IV was used in Formula Ford race cars. It can keep up with the rpms. That is not your problem.

jason

2000xp8 · Feb 18, 2006

Is this a solid lifter setup? Running hydralic up that high doesn't always work that great, if at all sometimes.

I've seen the stock computer go well past 7000 (obviously not in my car), with only Maf numbers and rev limiter delete in the chip, nothing special or fancy.

Is your block filled? Sounds like destruction waiting to happen, especially if you are kicking the crap out of it.

If you don't get it fixed, you may want to downsize to an rpm II, maybe a bit smaller TB, and that will relocate some of the power to a more usuable rpm.

Is this a street car or race car?

As far a pms may be helpful in a car that runs that rpm, i just don't think it's going to fix anything.

Grn92LX · Feb 18, 2006

The PMS will allow you to rev to the rpm you want. I assume you are running afm hi rev springs set properly for that cam? Are you running titanium retainers?

The combo you have is a proven 10 second combo n/a. Quite a few guys on afm's customer car section running 10's and low 11's with similar combo's.

mustangmarks · Feb 18, 2006

Whats a PMS?

Grn92LX · Feb 18, 2006

mustangmarks said:
Whats a PMS?

http://www.andersonfordmotorsport.com/pms/pms-50.html#pms

8URVETTE · Feb 19, 2006

Yes the heads have titanium retainers and locks. The springs are what they need to be. I have no signs of valve float at all so this isnt an option. I've been running 110 with no apparent signs of detonation either. No the block isnt filled and yes its a time bomb wating to go off but I feel if I can keep the r's below 7300 it will last long enough. I do drive it on the street but not a whole lot. I actually have a video of the car shutting down. Anyone want to host it for me? Oh, as for the chip, it was tuned on the dyno but we still couldnt really get the shut off problem figured out. Part throttle drive is fine, car runs great!

vristang · Feb 19, 2006

8URVETTE said:
Part throttle drive is fine, car runs great!

This implies spark or fuel. I would lean toward fuel (pun intended).

8URVETTE said:
Its a 306 with apporx 13:1 compression. Ported tfs heads, n-91 cam, victor intake, 90mm tb, 4.56 gears, etc... !

8URVETTE said:
Fuel delivery isnt an issue. 255 intake with a t-rex. Fuel pressure stays the same throught this whole ordeal.

I am not trying to be a jerk but this is not enough info.
What size are the injectors? Fuel pressure may not drop at all if the injector size is inadequate.
What has been done to the ignition system?

If the injectors are of adequate size, then I would look at a FAULT with the ignition system. At 13:1 you may as well consider this a power adder motor, as that compression could be blowing out the spark.

It is very helpful to just put all of your major mods in your sig.

Good Luck
jason

2000xp8 · Feb 20, 2006

I don't think the t rex is needed here, sometimes it slows down a good 255.

Maryland Stang · Feb 20, 2006

When the car dies is the tach suddenly dropping or is it coming down with the engine RPM? If the tach suddenly drops it's an ignition/computer problem, if it comes down with engine RPM look somewhere else. I learned this while researching an intermitant stumble mine had.

Rick 91GT · Feb 20, 2006

Sounds like fuel or spark to me, we have taken a customers 310ci motor into the 8000rpm range with a STOCK A9L and a chip, however he did switch to a PMS....which is worth every penny personally.

For what it's worth we broke 2 stock blocks turning 7500RPM, 1 after 10 passes, one after less...

What do the plugs look like?

eec shuts off above 7k rpm?!?!

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