Large gap in hp/tq on dyno

[Rei_a]

Hi guys im trying to figure out what the heck is going on here with my car or maybe a tuning issue. I recently purchased a 2010 gt500 that came with a metco 2.6 pulley, adjustable idler pulley, JLT cf intake and pypes axle back exhaust. I took the car to a local shop and put down 489hp, 540tq. Numbers seemed odd to me. Ordered a tuner with a bama tune for said mods and took the car back for another dyno and tune session. Dyno with the bama tune was pretty much identical to the first dyno 490hp, 545tq. After being tuned on the dyno the car ended up at 510hp, 557tq.

Car has 37,000 miles on it. I checked the lower pulley and its the oem one. No odd noises from the car during WOT. I have never heard/seen what belt slip sounds like but I imagine I would see a spikey drop in power on the top end from slipping which is not the case. Found black rubber dust around idler pulley and cleaned all the dust around to see how fast it comes back. Pulls were done in 4th gear on a dynocom dyno. No headers no H/X pipe. Stock rear end as well.

I cant seem to find anyone with this big of a gap between hp and tq. Any ideas? AF was in low 11's.

 

[ZX6Ray]

I would find another dyno first to eliminate that from being a possibility. I've never heard of a dynocom dyno (All I've ever seen or heard of are dynojet or mustang) but either way I'm wondering why you didn't get a VMP or Lund tune in the first place which already have great reviews from the svt community.

Did you datalog it while it was on the dyno? Might be as simple as an ignition or fuel problem. When was the last time you changed your plugs and what kind are they/what gap are they set to?

 

[Rei_a]

I would find another dyno first to eliminate that from being a possibility. I've never heard of a dynocom dyno but either way I'm wondering why you didn't get a VMP or Lund tune in the first place which already have great reviews from the svt community.

Yeah my local tuner said he could only tune my car through diablo so I went with diablo. Wanted local help whenever I needed it which turns out to be of little benefit currently. I will schedule another dyno test elsewhere to confirm results.

Yes my tuner data logged during pulls and didn't mention any fuel or ignition issues. I have owned the car less then a week and will pull the plugs tonight to check condition.

 

[Silver_Serpent]

I would find another dyno first to eliminate that from being a possibility. I've never heard of a dynocom dyno (All I've ever seen or heard of are dynojet or mustang) but either way I'm wondering why you didn't get a VMP or Lund tune in the first place which already have great reviews from the svt community.

Did you datalog it while it was on the dyno? Might be as simple as an ignition or fuel problem. When was the last time you changed your plugs and what kind are they/what gap are they set to?

Bingo. Change the plugs to cooler plugs and gap them if you havent already, and most importantly, get a tune from someone who knows how to tune these cars.

 

[lsp408]

I have 2012 gt500 with VMP 2.59 upper only and mail order tune from justin. It made 538hp and 545torque

I am running stock plugs without any issue

Not sure about diablo, but you should change to SCT. I heard sct has most available tuning parameter compare to diablo

Give VMP a call and they will be able to hook you up

 

[Mach828]

What is going on with that air fuel ratio! Good god

 

[rotor_powerd]

You'll be needing a rebuild before long if you continue to run the tune that's on it, judging by the air fuel ratio. Get that taken care of ASAP.

 

[blackvette101]

sorry but any tuner that see's the AFR climb like that after 5k rpm and decides to keep going with the pull is retarded. Seen a few motors blown that way. Your not making power because the car went lean and the ecu pulled timing in an attempt to save it.

Its hard to read but it looks like 13:1 afr when he was still in it at 6k rpm.

 

[Rei_a]

sorry but any tuner that see's the AFR climb like that after 5k rpm and decides to keep going with the pull is retarded. Seen a few motors blown that way. Your not making power because the car went lean and the ecu pulled timing in an attempt to save it.

Its hard to read but it looks like 13:1 afr when he was still in it at 6k rpm.

I asked him about the af climbing like that and he said everything was fine. I will go ahead and flash back to the bama tune for now though.

 

[TORQJNKY]

sorry but any tuner that see's the AFR climb like that after 5k rpm and decides to keep going with the pull is retarded. Seen a few motors blown that way. Your not making power because the car went lean and the ecu pulled timing in an attempt to save it.

Its hard to read but it looks like 13:1 afr when he was still in it at 6k rpm.

I completely agree. This is exactly what I was about to type. OP, what is your fuel system set up? Looks like you are running out of fuel up top.

 

[07 Black Beauty]

Do yourself a favor and get a Lund or VMP tune.

 

[black2007shelby]

check this one out op
[URL="


11.7 afr near the end of pull.
Stay steady not climbing . This is with 56lbs injectors and no bap though. Hope this help

 

[Rei_a]

I completely agree. This is exactly what I was about to type. OP, what is your fuel system set up? Looks like you are running out of fuel up top.

Stock fuel system. Only upgrades are 2.6 upper pulley, jlt air intake, axle back exhaust.

 

[Rei_a]

check this one out op
[URL="


11.7 afr near the end of pull.
Stay steady not climbing . This is with 56lbs injectors and no bap though. Hope this help

Thanks that looks like a very solid af ratio.

I'm starting to gather the general consensus is I should retune with a proven tuner and see what kind of numbers I get.

 

[black2007shelby]

I used to have the same setup as u rei.a but with a mail order jonlund tune and sct x3 handheld from evolution. When i put it in the dyno for the very first time, it made 536 hp , 496 torgue without adjusting anything. This is just dyno run and check afr. AFR like in the 10s. Mine tuner said its still running a little rich. After leaning it out a lil bit, we gain 25 lbs. torque across the whole powerband. Car drive better than before. So i think u should call vmp or evolution to get a tune and an sct. Or maybe try different dyno tune in ur area and have them check everything else. I think u can get the most power doing custom dyno tune though.

 

[99cobraUgotbit]

I had a local guy tune my car. He added too much timing and kept blowing my 02 sensors. So I went with VMP and haven't looked back.

 

[Sirraf]

If your tuner said it is fine, then run...far away. 13.1 is not fine.

 

[Rei_a]

Thanks guys for all the responses

 

[TORQJNKY]

Stock fuel system. Only upgrades are 2.6 upper pulley, jlt air intake, axle back exhaust.

I think you are maxing out your injectors. The stock 47lb injectors will usually max out duty cycle with an upper pulley and intake. I would consider a bigger injector, like black2007shelby had (56lb) or a BAP before you retune it.

Here's some good reading on that: http://www.vmptuning.com/forum/showthread.php?t=937

 

[black2007shelby]

I think you are maxing out your injectors. The stock 47lb injectors will usually max out duty cycle with an upper pulley and intake. I would consider a bigger injector, like black2007shelby had (56lb) or a BAP before you retune it.

Here's some good reading on that: How much power are stock GT500 injector's really good for? - VMP Tuning Message Board

OH no , i used to have the same setup as him with stock 47lbs injectors and no bap , when it first run in the dyno , mine tuner said its still a little rich making 536/498 for the first run on the dyno. The graph that i first show him is mine latest setup. That is with 56lbs inj. and tvs blower making 11.7 afr.