Help with car at a loss with whats wrong

[VanWilder]

Well to start off the car is running fine...but yesterday I went to my local performance shop to get a dyno tune to get ready for our local Midnight Drags tonight. I currently have a tune from Chris Rose at American Muscle. It made decent power but was down quite a bit from where I should be. Last April, I believe, I dyno'd at 328rwhp/306rwtq on this tune with A/F right at 12.9-13.0 out the tail pipe on a DynoJet...yesterday I strapped it on a dyno again (DynoJet but at different place)...and with no changes made to my tune I only put down 306rwhp/289rwtq at 13.80s A/F...so of course I was very confused as to why my car lost so much power with no changes...but we continued to try to tune the car and make the power it should...after 4 hrs of dyno tuning the most we could get out of the car was 308rwhp/306rwtq with A/F in the 12.70s...we messed with adding fuel and subtracting fuel with no luck...we messed with timing adding and subtracting again with no luck...i'm at a loss...what could cause this?! any help is greatly appreciated...

side note: we thought maybe I fouled a plug so I pulled them but dont know how to read these damn HT0s...maybe new plugs are needed...maybe a bad coil...how can you check the coils?! Also while at WOT fuel pressure was at a constant 40psi...is that where it should be?!

Sorry for all questions just wanna get this figured out

And just for clarification this tuner has done numerous mustangs and another car that I know of with the exact same mods as me and made 349rwhp/330rwtq so I know he can tune the car.

-Lance

 

[mac10chap]

Honestly, you said all the suggestions I would have. Start with the plugs. I doubt it is a bad coil. I just recently had a coil go out on me and it was idling pretty rough and threw a code. I would first, check the gap of your current plugs and make sure they are still gapped at what they should be. If so, buy a new set, gap them, and see if that fixes it.

How long has it been since you cleaned your MAF and T/B?

 

[VanWilder]

Honestly, you said all the suggestions I would have. Start with the plugs. I doubt it is a bad coil. I just recently had a coil go out on me and it was idling pretty rough and threw a code. I would first, check the gap of your current plugs and make sure they are still gapped at what they should be. If so, buy a new set, gap them, and see if that fixes it.

How long has it been since you cleaned your MAF and T/B?

Ok thats what I was looking at doing...just didnt wanna spend the $80 for new plugs if not needed...its been probably 2 years since I cleaned the MAF and T/B but only probably 3000 miles...dont drive the car often

 

[mac10chap]

I hear you but new plugs is never a waste of money. If it doesnt fix it, no need to try and recoup money. You can always stash them away confidently knowing that you will need them soon enough anyways.

 

[VanWilder]

Here are some pics of the plugs...just to clarify I had Copper Anti-seize on these and thats why they have a darkish orange look in some pics

 

[VanWilder]

I hear you but new plugs is never a waste of money. If it doesnt fix it, no need to try and recoup money. You can always stash them away confidently knowing that you will need them soon enough anyways.

Yeah thats true...didnt think of that

 

[The Big Herm]

If it was a plug fouling problem you would see bumps on your dyno sheet. It is always good to check the plugs, but I dont think that is your current issue.

 

[mac10chap]

How did the weather conditions differ from the previous dyno to this one?

 

[SteveP]

What were your IAT's, Coolant temp, temp outside, fuel. All these take a huge part in it as well. Was he SAE or STD?

 

[VanWilder]

How did the weather conditions differ from the previous dyno to this one?

They were pretty similar...

 

[lostsoul]

What were your IAT's, Coolant temp, temp outside, fuel. All these take a huge part in it as well. Was he SAE or STD?

+ 1 I have see my HP drop like a rock from temp changes and heat soak.

 

[VanWilder]

What were your IAT's, Coolant temp, temp outside, fuel. All these take a huge part in it as well. Was he SAE or STD?

I'll have to have him check the datalogs...but if I remember correctly...IAT was around 68, Coolant Temp 172 or so, outside was cold...probably 45, and fuel was 93 octane Phillips 66 I believe...I'll check if it was SAE or STD...I would assume the number were STD

 

[AlbertD]

I would suggest running it at the track and see what you trap. I have dynoed at several places and seen as much as a 25-30 rwhp difference.

If your trap mph is considerably different then I would suspect a problem.

 

[VanWilder]

I would suggest running it at the track and see what you trap. I have dynoed at several places and seen as much as a 25-30 rwhp difference.

If your trap mph is considerably different then I would suspect a problem.

I thought of that...would you suggest just running NA are would you spray it too...cuz if I run tonight it will be very hard not to spray since I have a nice full bottle I had prepared to use

 

[JeremyH]

Could be dyno differnces. I agree grab some new plugs especialy when running nitrous plugs dont last too long, check the gap on the current plugs as well.

 

[VanWilder]

Could be dyno differnces. I agree grab some new plugs especialy when running nitrous plugs dont last too long, check the gap on the current plugs as well.

I thought about dyno differences...but last time I got it dyno'd I did it on two different dynos as well...one dynojet and a superflo...both made basically the same power within 1-2...I wouldnt think a dyno would rob 30hp and 25tq...especially since a buddy with equal mods on same dyno made 349rwhp/330rwtq...I will check plug gap though and get some new ones

 

[california gt]

i am no expert but what does your "seat of the pants dyno" tell you?
If it still feels strong and your happy.........

i think most, not all, can drive themself crazy with numbers. me included. my 2 pennys.

 

[VanWilder]

i am no expert but what does your "seat of the pants dyno" tell you?
If it still feels strong and your happy.........

i think most, not all, can drive themself crazy with numbers. me included. my 2 pennys.

I can agree with that...the thing that is bothering me the most is the fact that when tuning we couldnt pick up any power no matter what we did...the graphs matched every run almost to a tee...seat of the pants wise it feels fine but I dont know how long its been messed up if it is...also from my original tune it had leaned out a lot on my base pull compared to my previous dyno session...went from consistent 12.90s-13.0s to 13.80s...and we checked my A/F gauge in my car compared to dynos sniffer and they were basically dead on

 

[AlbertD]

I thought of that...would you suggest just running NA are would you spray it too...cuz if I run tonight it will be very hard not to spray since I have a nice full bottle I had prepared to use

I would run N/A first, if all seems well then spray away.

 

[VanWilder]

I would run N/A first, if all seems well then spray away.

Thinking about it..but kinda scared if something really is up with it...cant afford to blow anything lol