Ford Mustang Forums banner

Ran into a wall at 5500 RPM on the dyno

4K views 63 replies 17 participants last post by  Ed Curtis 
#1 ·
Hey guys, I need some help. I finally got my car to a dyno to get a dynotune and he had no problems until he made a full pull and for some reason, the car fell flat on its face at 5500RPM. He checked the tune and the Rev limiter was set to 6500 RPM, the speed limiter was set to Max and the catalog showed the car going rich when the issue happened. We bypassed my MSD 9A and same issue happened. We tried a pull in 3rd gear and same issue happened at the same RPM. We increased the Rev limiter to 7000 RPM and same issue.

What could the cause of this be? The tuner said it almost felt like the timing dropped to zero but his datalog showed constant target timing...

Here's the video:
https://youtu.be/X5jAGS5ei8w
 

Attachments

See less See more
1
#4 ·
Sorry, I don't know why my signature didn't show up. It's a 347 with ported TFS TW heads, Ed Curtis cam, Victor EFI intake, 42 lb injectors, etc. The tuner used an SCT chip.
 
#3 ·
I would look into the TFI since it controls dwell. Latency? The PIP could be suspect too. How’s the battery and alternator voltages, fuel pressure, fuel regulator stock or aftermarket? Any vacuum leaks? There could be so many things.
 
#5 ·
I believe it's a new TFI module and an MSD billet distributor. Latency of what? The car is healthy until exactly 5500RPM...cooled it down multiple times and still a very consistent wall. Stock fuel pressure regulator and no vacuum leaks. We're better it's a spark or timing issue but it almost feels too consistent.
 
#9 ·
So what’s the rest of the ignition setup? New coil, tfi, distributor? Battery voltage look good?

Fuel looks good so I don’t see it being that. I’ve had issues with spark breakup before, although a little before 5500 and it ended up being a faulty tfi I received from Davis. Replaced with a motorcraft unit and the car revs clean to 6700 now. Not saying this is for sure your problem.

Do you know which program your tuner uses?
 
#10 ·
It's a newer Standard TFI (probably not the best quality). Unfortunately there's no way to share the datalogs. MSD dizzy, coil, and 6A.
 

Attachments

#11 ·
You're going to need to do the crystal mod on the stock computer if you're trying to rev to 6500. I had to do it for both of my cars and they pull to 7400 with a a9l. I tried everything and that was the only thing that solved my problem. My cam was ground for a 7k shift point, so I had to get it done or go stand alone
 
#13 ·
I'd try a Ford distributor before messing with anything else. If you can't find one at a junk yard, I should have my old one in storage.

Also, you might consider asking him to change his correction factory to SAE instead of STD, since it seems to be what everyone uses these days.
 
#37 ·
I'd try a Ford distributor before messing with anything else. If you can't find one at a junk yard, I should have my old one in storage.
My son's 94 GT was never right after he installed a new distributor from Oreilly's, it looked nice, but that's where it ended. Buddy of mine is a tech at a performance shop in Pensacola, and has had the same issue with those distributors sourced from that off-shore company.
 
#14 ·
I have a performance distributor hot forged in my car and it never skips a beat. I’d recommend one, plus they’re a bit cheaper than msd, not that I’ve ever personally had issues with msd parts. Hell I run one of their coils.
 
#19 ·
I have a Pro M 80 mm calibrated for 42 lb injectors so I shouldn't be anywhere near outflowing the MAF.
 
#26 ·
If your tuner won’t share tune files or data logs then I wouldn’t go thru him. What’s the point of paying for a tune if you can’t get the file, and can’t get data logs for dyno time you paid for? Sounds like some bull#### to me.
 
  • Like
Reactions: tmoss
#28 ·
I'm going to try replacing the TFI module and distributor to see what that does and report back.

Thanks everyone!
 
#30 ·
What would you do? There's obviously an issue with timing of spark (it doesn't sound like it's hitting a Rev limiter where RPMs are oscillating) and the tuner can't give me datalogs (the tuner said commanded spark advance looks fine, fueling via AFR is fine, and I have a brand new flow chart from Pro-M saying there's not a dead spot and there's no possible way I could outflow this MAF) and it's hard as hell for me to diagnose issues at 5500RPMs.
 
#31 ·
i would diagnose, that is what i would do.

and the flow chart means nothing, when a limiter within the strategy can be hit

that is why one datalogs

if you suspect its spark, take a it to a shop, why the dyno place does not have one, is besides the point, with a scope, and look at secondary wave form linked to the firing order

that would tell you 100% if spark/timing is an issue

there is NO excuse, for swapping a part that isn't first proven to be faulty

How do you know fueling is correct, if you cant see lambse to compare to your recorded AFR??

also with respect to rev limiter, do you know how the EEC controls the rev limit?

And regards to the "commanded timing"..........that is ALL IT IS.......

what if the SPOUT is NOT connected.......guess what your timing could be commanded to 26deg all day long and you only have base timing......

How do you KNOW? looking at it, with a timing light..........
 
#33 ·
96p ushrod has the right idea. Buy the tools that will help you. You can buy a used qh on here the other day for 165 dollars and a wideband for 200 bucks. Dechipia will tune the thing for next to nothing if he even charges you. You can answer most of indys questions as well. Both those guys are a wealth of knowledge.

If not you have to throw parts at it and most likely fix nothing. If your above post is 100% correct. Your eec did not pull fuel or timing then the rev limiter is fine.

However is your timing 100% correct. Did you use a degree wheel and piston stop to find TDC and set you pointer? Does your tuner have a lab grade o2 sensor that is cal'd ?

You can always grab a timing light and point it at your hand and look for an even flash, then rev it to 5500 where your wall seems to be. Flash should be faster and still even.

If not your call
 
#34 ·
So I had a TWEECER before and got it to run with Deciphas website (super awesome knowledge base so thanks Decipha and also thanks Indy for answering my questions via PM when I was going that route) but I just didn't have the time to tune not is the car registered to test on the road. I'm going to Rev it in my driveway to see if I can feel the wall without load. If I can, I'll get my friend to Rev it while I watch a timing light. I'm also thinking of throwing the TWEECER back on with my previous baseline tune to see if the wall happens.

The tuner said he disabled EGR but could me forgetting to remove the wideband signal from the EGR pin cause issues like this?
 
#38 ·
Yes, no EGR.

why isn't your tuner using the logs to tune?

sounds very fishy......

you look at places like lund, that tune using the datalogs the customer provides
Nobody said there were no datalogs. My tuner doesn't know how he could send them. I saw him datalogging and I trust this is not a tune issue.
 
#40 ·
I don't remember what valve springs I have but if it was a valve float issue, the float would be erratic on the Dyno graph right?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top