I am posting this here because there is more of a chance of someone actually knowing what they are talking about here than in Tech.......I do not want misinformation ruining my buddy's $60,000 Shelby Cobra

a friend of mine's Shelby Cobra with a FAST ecu has a problem

first, here is his setup

427 punched and stroked to a 464 with ITB's and 34lb injectors

recently put down 608whp and 689wtq conservatively

I would not be asking for help if the car was corroborated because I am experienced with a carb. I have never messed with F.A.S.T. and I have seen that some people have problems with the quirkiness of the system. especially with MSD ignitions (which is what he has)

he was driving it three days ago and the car suddenly lost power. There was no hesitation nor was there any mechanically failure. I just checked the car out tonight and found a few things that are array. First of all I will say that the distributor was tight and did not show any signs of movement (it was marked)

I checked for adequate fuel pressure and there was more than enough.

I came to a conclusion that timing has somehow advanced to an extreme amount.....so far advanced that there was spark before fuel was in the cylinder. I hooked up timing light and found that timing was ALMOST TO 45* BTDC

I immediately loosened the dizzy and adjusted timing to a factory 8* BTDC and the car ran......barely (very very high lift/duration cam). My question is, what would cause this sudden jump of timing.....especially on a distributor driven car. I removed the distributor to find no signs of tooth wear and if the timing chain were to be off a tooth then there would be other SERIOUS problems, especially with such a high lift cam.

what would you guys think would be the root of the problem......do you think that the F.A.S.T. system could alter the timing to that far of an extreme.

BTW: he had a problem with a header leak and since he has the F.A.S.T. system equipped with WBo2 it detected the problem (too much o2 in the exhaust from the leak) and put it into limp mode.....I fixed the problem as of yesterday and now I have to figure this out. I have his original program from when it was tuned and I have the current logged program of it running now (yes, I did get it running and I did a five minute log to compare with). I will be comparing settings and specifications in the dyno log book and hopefully that will point me int eh right direction.

Thank you for taking your time out of your day to help me and my buddy Bill.

-Daniel Beard


Modified by DirtySol at 6:33 AM 11/12/2004

 

 

You might also want to try the NASA forums, or whatever the Factory Five Spec racer forum is, there'll probably be more guys used to dealing with V8s there.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DirtySol &raquo;</TD></TR><TR><TD CLASS="quote">My question is, what would cause this sudden jump of timing.....especially on a distributor driven car. I removed the distributor to find no signs of tooth wear and if the timing chain were to be off a tooth then there would be other SERIOUS problems, especially with such a high lift cam.
</TD></TR></TABLE>

I'm afraid I can't be of much help, but here's some food for thought:
is that engine an interference engine? 'cause if it ain't, you may have jumped a tooth, and it won't break anything, even with a high lift cam.

 

Did you try the Drag Race forum? There's plenty of top name guys in there that make a living tuning FAST and know a thing or two about V8's and tuning them.

 

Nothing wrong with 45 degrees of advance at low load... how did you check it, exactly?

Did it still idle after you changed the timing, oh, 37 degrees!!!??

Anyhow, check the advance tables in the map currently running the car. It could be that there's nothing wrong with the timing.

Big 'ole V8's need a crapload of timing. NA they usually take 35-37 degrees at full load, full RPM, so an extra 10 at idle isn't that alarming.

Jon

 

hrmmm, no

a Corbajet 427 FROM FACTORY requires 8-10 degrees of timing......yes, it WILL run with 30 degrees of timing but as soon as you put a load on it, it WILL backfire.

timing advanve tables are usually set around that with a load in the upper 4000's but timing at the distributor at idle shoud not be over 14 degrees at most

yes that much timing is VERY alarming.......c'mon guys, engines are not as yough as you think they are.

*sigh*

 

go to http://www.bandtmotorsports.com they are a local tuning shop in northern va and they deal with FAST almost exclusively... they tend to know whats going on.

 

A cobrajet(?) from the factory didn't come with ITB's, or punched to 464, or with a F.A.S.T ecu, or put down 6xxhp, so I don't know where this "factory" specification of 8 degrees came from.

The timing is controlled by an ECU, isn't it? As soon as load increased (as sensed by the MAP sensor). It's likely that the timing will back off into a more reasonable amount...... possibly. Depends on the map.

I'm not trying to lead you astray, just trying to (politely) point out that it may not be as simple as that.

Good luck,

Jon

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MMsportsRexSi &raquo;</TD></TR><TR><TD CLASS="quote">go to http://www.bandtmotorsports.com they are a local tuning shop in northern va and they deal with FAST almost exclusively... they tend to know whats going on.</TD></TR></TABLE>

THANKS!!!!

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jon Nelson &raquo;</TD></TR><TR><TD CLASS="quote">A cobrajet(?) from the factory didn't come with ITB's, or punched to 464, or with a F.A.S.T ecu, or put down 6xxhp, so I don't know where this "factory" specification of 8 degrees came from.

The timing is controlled by an ECU, isn't it? As soon as load increased (as sensed by the MAP sensor). It's likely that the timing will back off into a more reasonable amount...... possibly. Depends on the map.

I'm not trying to lead you astray, just trying to (politely) point out that it may not be as simple as that.

Good luck,

Jon</TD></TR></TABLE>

I understand what you are saying, but what I am saying is this........

lets say that you were to take and sleeve a b18 to 85mm and install some ITB's and use Power FC........wouldn't the distributor settings still be the same.

see what I am saying.....I was not talking about the ignition maps being that far off I was talking about the distributor itself being that far off........it would be like a B18C5 having its timing set at 35* BTDC.......sure it would run, but once it started to accel or have ANY load it would immediately die and/or backfire

 

Well how do you accurately check timing on a B series? By jumping the service connector to make sure the ECU does not change ignition timing. Is there a similar procedure with this particular ECU to get true base timing? Also, an MSD may not give accurate results with an inductive timing light, since it obvously delivers multiple sparks per combustion event. Just some food for thought.

If the dizzy has not indeed moved, and the cam has really not jumped a tooth, then to me that says ECU(possibly a bad tune?) problems.

 

found out what it was.....somehow the ECU's timing map got all screwed up.....it was really wierd