Analyze my dyno-1999 GT Auto

[Red35th]

Hey all, I need some questions answered about my dyno graph.

I think, so does my cousin that the dyno was a little low, thoughts?

Why does my hp DROP! after 4900 rpms? It looks like my engine just dies right there. And why does it get so wavy also, the rest of the graph is smooth.

Why is my 2nd run so much worse than the first? Does the EEC-V cut timing when it's hot?

Thanks a million. Any comments/thoughts are appreciated. And if your are in Huntsville, AL, check out Trackmasters. Real nice guy. Only $60 for 2 or 3 pulls w/ A/F. Anyone with another similarly modded auto want to post up theirs?

 

[007]

The hp numbers are perhaps a few hp on the low side, but no big deal. I have the same set-up really with the additional of pulleys and timing adjustment (proven mods) and 4.10s that only hurt a little, and my car made 232rwhp and 271tq. I dont know if thats corrected (hot day) or not tho, and its not great for an auto with my mods...

Your A/F ratio gets a little low at the top end for an NA car, but I dont know why the sudden kink is present in the curves..?

You should be making more power near the 6k rpm range.

 

[DC-GT]

It looks like it runs out of flow at around 4850 rpm's. Where it is restricted is the next question. Are these the 99+ PI heads? There are lots of things that could effect these readings...

TPS is maxed so it is telling the puter to dump max fuel in and the mix is not all too bad although a tad rich for N/A. I would say try a plenum and 75mm throttle body (assuming that is applicable to your version of 99). That combo leaned mine out on the dyno N/A. I bet you would see a pretty good gain from that alone. If you have non-PI heads they will still be holding back some flow. When you start talking heads your looking at a bit of $$ though.

Hope that helps some!

Bo

 

[trinity_gt]

Red35th, you're not the only one who's noticed that their PI modular appears to have a power peak a few hundred RPM below the peak advertised by Ford which I think is 5250. During dyno pulls last summer, my stock(ish) GT also peaked in the high four thousands. Even after a couple of simple mods (pullies & the K&N FIPK), it still wasn't peaking where Ford said it should.

http://home.golden.net/~trinity/Dyno/pulleysdyno.jpg

I'd be willing to accept the explanation in my case is friction from a relatively new & therefore tight engine but, at the time, it had about 15,000 miles on it and I'dve thought it would have loosened up by then.

Having said this, I'm not unhappy with the car or where its power peak is.

Why yours has such a sudden drop is a bit of a mystery. Perhaps a bit of spark knock set in and the PCM pulled some timing out.

 

[Red35th]

Yes, I most definatley do have PI heads. I always thought that I needed to move my shift points up, but the graph shows otherwise. Why does it get so wavy after the peak??

And dyno gurus, any idea how much hp could be gained with bumping the timing and leaning out what you see?

Thanks again.

 

[e3troy]

My first dyno with a mac cai and flowmaster catback gave about the same hp numbers. The avg of three runs was 217 hp (not sure of rpm) but my torque was quite a bit higher at 259. Mine is also a 1999 Auto. After reading your sig, I also ran a best of 14.2 in the quarter with that combo.

Troy

 

[Redfire03GT]

Why is the torque reading so low? Shouldn't that be higher, even considering it's an automatic?

 

[Red35th]

Those were my thoughts also. I'll tell you though, it feels alot torque-ier than the dyno says. I think the torque convertor skewed my run. When we did the dyno we punched it in third and it dropped it to second, I don't know if that affected the run.

Does anyone know why the squiggly line and and sudden drop in tq/hp occurs after 4900. I really don't think it's my heads and intake exhausting. Any answers?

 

[e3troy]

Yeah, it probably has something to do with the car being an auto. I've had my car dynoed by two different people and both complained about not being able to slowly accelerate into third and then stab the throttle without the car downshifting. Both people said that's why my torque curve never appeared flat because they had to ramp up to speed so the car didn't downshift. It may be the reason your torque numbers are low. And since hp is calculated from torque, it would explain that too.

Troy

 

[lopey4.6]

If your getting a chip burned the tuner can make the torque converter lock into a certain gear to eliminate downshifting. Also I think you can get at least 10 rwhp from leaning out the AF

 

[LI98GTStang]

http://forums.stangnet.com/showthread.php?t=379986

Here is a thread with more dyno sheets (including mine) on mostly stock mustangs for comparison. Your HP is pretty much right on, but agree with Redfire that the torque numbers look low. Just making sure, that the OD and traction control was off. My car is a 5sp, so I can't offer up any suggestions for personal experience.

 

[Red35th]

Thanks 98GT for the link. It only confirmed my suspicions that the dyno run went wrong. I still haven't seen a dyno from a 99-up that peaked so low, and then fell so fast. I blame the car shifting from 3rd to 2nd to 3rd for the screwy torque.

Why does my car die at 4900 rpms?