My experience on a chassis dyno with my Turbo 2.3 T-Bird

I know this is not BBF related, but some of you guys have dyno experience so here goes.
I am a bit puzzled on this...I am trying to figure out what is going on.

On Sunday, between the 1st and 2nd rd. of Open Comp @ the NMRA World Finals @ Beech Bend, I went over and made 3 dyno pulls with the 2.3 Turbo  T-Bird and after my 1st pull the dyno operator called me over and said something was wrong with the car. The power suddenly stopped @ 4800 and just leveled off. You can hear the engine in the video take off and stop climbing when it hits 4800 and sounds flat, then the rpm slowly climbs. He took it to 6000 because that is what I go thru the traps at.
All pulls were in high gear.

So for the 2nd pull I fattened it up a hair above 4600. This time I was in the passenger seat logging the AFR numbers and watching the AEM wideband. Wow ! I really felt it in the car when it hit the wall @ 4800 on the rpm climb. Same results as pull 1 but he lifted at 5500. No change in the power

So at the advice of the dyno operator I swapped out all 4 plugs for new ones. Same exact thing happened again. No change. My fear was an electrical problem, and since I am going to attempt to set the P/SA record this coming Sat. @ Indy, there would not be time to swap out the ignition system and re-test.

So my only chance to see if I had a problem was to run the car in round 2 of Open Comp and see if the car runs a normal time at that weight in those weather conditions. The car ran great and felt great to make my quickest and fastest run of the weekend and those were normal times at that wt. and weather conditions. My afrs have been the same all year long with that head and those drop-in springs. We are not allowed to run double springs...only single with a damper. The engine has a hyd. slider cam @ .400 lift and the boost is in the mid 20's. The current seat pressure is 115 @ 1.56" installed ht. and 215 lbs. open @ .400 max lift.

I have been talking with other racers trying to figure out what caused that engine to do that in all 3 pulls. Just hits a ceiling hard on the power curve.

One theory was tire spin.
Another was that the rate of rpm acceleration with was too quick on that dyno and possibly "rattled" the valvetrain. ( I can kind of see that)
You can hear the engine bog for a second then slowly rise in rpm and the  dyno sheet shows it.

Color me puzzled on this one...





1st pull all the way to 6000:






2nd pull to 5500:

Electrical, Fuel or springs giving up?

Don't try and fix something that may not be broken in a few days. I would leave it alone if the E/T's and MPH are normal.

Springs is my guess. How many passes on them? Could the turbo be stalling? or surging? starving for air?

IMO if the problem only showed up on the chassis dyno, but didn't show up when the car ran down the track with no problems, then the problem has to be something somehow related to the car being on the chassis dyno.

Thanks for your input guys.

dfree383 wrote:Electrical, Fuel or springs giving up?

I ruled out fuel delivery because my air fuel ratios and fuel pressure looked good, but I did suspect electrical at first.
Some of the 2.3 guys think it was the valve springs.

supervel45 wrote:Don't try and fix something that may not be broken in a few days. I would leave it alone if the E/T's and MPH are normal.

Yeah, after those dyno pulls, the Bird ran it's quickest pass of the weekend and I was relieved.

Still would have been nice to see where the curves peaked, so I could determine a shift point. I will never know now.
Just have to experiment.

jbozzelle wrote:Springs is my guess.  How many passes on them? Could the turbo be stalling? or surging?  starving for air?  

Yes John, those springs pressures came to my head right after the possible electrical deal. I have super soft numbers to start with and when you push 37-40 lbs of additional pressure on the backside of the intake valves from boost, that doesn't help any.

That turbo has made more power than that before. I have ran as high at 113 mph with a different head and intake but with the same turbo, injectors, and tune and weight. I am only running 110 mph now at the same weight.

DILLIGASDAVE wrote:IMO if the problem only showed up on the chassis dyno, but didn't show up when the car ran down the track with no problems, then the problem has to be something somehow related to the car being on the chassis dyno.

I now think you hit on the problem Dave. One theory was the weight of the drum is lighter than the car going down the track in 3rd gear. I know it spun up pretty fast in 3rd on the dyno and on the track it takes along time to go from 4700 to 6000 in 3rd after shifting out of 2nd.

I'm leaning towards springs. I built a bunch of those 2300 for dirt and they need more spring than that n/a. With the boost your running I doubt 110 lb seat is enough. and at .400 lift how close to coil bind are you. Are you sure of the nose pressure?

It has probably been doing it all along, you just saw it on the dyno.

I have a 87 ranger with a 2300 turbo coupe engine in it lowered front and rear, hybrid turbo, ported head, roller turbo spec cam. Its running just needs the intercooler mounted and plumed and the MS II added and tuned.

I may give you a shout when the tuneing starts.............

Just saw the 215 # open, I don't think thats enough.

I tend to agree with you on the spring pressure deal Blake.

This weekend I found out part of the reason my engine was down 2 lbs. of boost. ( pic attached)

The car ran a 12.34 to set the P/SA record at Indy Friday afternoon, but it should have ran a 12.15 if the boost had been correct.

Now....this raises more questions. I doubt the hole in the header had anything to do with the dyno deal. But it would explain why my top end mph was off, and I had been blaming the valve springs all this time.
It may have been both problems at the same time.

To get even more confusing, this past weekend my friend ( and previous owner of my Turbo Coupe) ran the quickest time ever for a 2.3 Turbo Stocker ( 11.39 ) and set the N/SA record.

He does not think it is the springs causing my problem. His spring pressures are not far from mine and he must be making close to 40 h.p. more than I am. Same fuel, cam, intake, trans, etc.

Could not see this on the car, but after tear down and on the table it was obvious. That would explain the low boost problem.

Any leak on the header will hurt hp. That very well may be the problem.

That's what I thought.
That car ran a 12.26 @ Bowling Green in May of this year when it was 175 lbs. heavier.

So sometime in the last 4 1/2 months that hole started and gradually got bigger and bigger.

I won't know until next year if the car will come right back to where it was after patching the hole. Our season is over now.
I have another ATR header ( new) that I am seriously considering sending to Nitro Plate and see if they can coat the inside as well as the outside.

I think that corrosion may have been caused from running the car cool all the time and using C16.