Most people run an idler with anything smaller than a 2.93 pulley. Your belt is also too large. 96stanggt is spot on.
Dynoed pulley/intake/catback; Questions...
- Thread starter kilrb
- Start date
I checked back in with my shop, and described the tensioner, and they agreed it's not right. They told me to come in Monday, and they would throw on the right belt, and re-tune. Everyone I talked to there agrees the numbers seem low. I'll post up after we re-dyno.
Out of curiosity, if the problem is the belt size, and pulley-slippage, why doesn't it appear in the dyno as an oddity? Would it be a nice, even slip that affects low end torque as well as high-end? I always thought belt slippage appears as a sudden drop in torque...
You are right prolly in the 430-450 range.
To the OP hope you get everything figured out!
Just took the vert out to breakfast, and on the way home, I was watching the boost gauge. I'm pretty sure I can see it slightly dipping in the high rpm range, but more importantly, it looks like the boost is only going up into the 12 range. At lest, that's where I estimate it to be after looking at the Hilton overlay pictures on this site. The only thing I don't know is, where does the factory stop pin peg the factory boost gauge? If it's 10, then mine must have been trimmed, as it's going well above the 10 mark, but it's definitely not going to where 14 would be on the Hilton. Don't konw if this definitively proves anything or not...
Sorry but you will need to either buy an aftermarket gauge and install it OR get the overlay and borrow/buy a gauge to calibrate it.
I got the Cobra back in to the tuner yesterday, and they threw a new belt on it. They brought in a couple of different belt sizes to make sure they had what I needed, and they started with a 73.5" belt, which they couldn't get on. They wound up getting a 74" belt on (the first was 74.5"), and the tensioner now sits closer to the center than it did before. They told me to throw the 74.5" in my trunk to use as an emergency back up. The guy who did my tune was not in, so they just put the belt on, and told me he'd get in touch with me to throw it back on the dyno and re-tune if necessary. I also ordered the Hilton Boost overlay yesterday, and will put it on as soon as it arrives. I'll post back up after the car gets back on the dyno. As far as driving impressions go, I hate to even comment, because SOTP is so subjective. It felt as if it might have been a little bit feistier, but my subconscious mind plays too many tricks on me for me to believe it without seeing the dyno #'s... 
after your retune, I think youll be pleasantly surprised!
You really should get the auxiliary idler put on with the different belt running the 2.8 upper. From everything you're saying about this tuner I'd take my business elsewhere. They seem to be feeding you a load of bs every time you talk to them and you keep eating it up. The info that member's are trying to give you here is correct and yet you keep ignoring it and just waiting for the "tooner" to tell you what they want to do. I'd be pissed off big time if they made those stupid mistakes on my car after having "supposedly worked on 30-40 cobras". This is simple mods they're doing and they sound like they're clueless.
I'm posting on this board because I respect the knowledge of the members here. Although I haven't responded to every single point made by every poster, I haven't ignored a single comment made by anyone. I have dealt with this shop for three years on my LS1 Vette, and I respect their knowledge, although I do understand that they are not the end-all-be-all, and I do understand that they can make mistakes both big and small. The bottom line is, I don't know how to custom tune a car, and I don't have a dyno, so I need to partner up with someone. I'm not going to "fire" this shop because they put on the wrong size belt, and go off to a shop I haven't even heard of for a tune. I'm working to incorporate the information I get from you guys into a path forward. If I come to a logjam with this shop, then I'll move on, but I'm not there yet.
The idler question is a good point. Many people replying to my thread have strongly advocated adding auxiliary idlers to reduce belt slip, and I'm definitely paying attention to what they are saying. At the same time, I have read several posts of people with auxiliary idlers who have encountered slip, and an article on mustang50magazine.com where they put on a 2.8" upper without auxiliary idlers, and reported no issues with slippage. The shop I'm using is more than happy to install the aux idlers if that's what I decide to do. I'm not ruling out doing this, but at this point, I want to get the car back on the dyno, have it re-tuned, and see how it goes. I also will watch for belt dust to see if I'm having issues. I would still appreciate (and need) the input of the members on this board.
I really think you need to find a new shop. They claim to have done so many Cobra's, but it really doesn't sound like it. An upper only setup is a very common and simple combo. That belt is still too big, when I ran a 2.75 pulley and 100mm aux idler that's what size I ran. If you're not running that idler then the belt will be too lose. Need to get some datalogs to really see what's going on, did you ever pull the plugs and check what kind and gap?
So I went and looked under the hood, and looked closely at the belt tensioner. It appears to be almost, but not quite, pegged against the tight end, which to me suggests the belt is indeed too long. Am I correct in this assumption, or does this not really prove anything? Thanks.
the belt in the pic, is not a gates.
I'll request that they e-mail me the datalogs from the next dyno run for you guys to review. What format are those posted in? I believe I can datalog with the SCT handheld I bought for them to upload the tune, right? I'll see if I can figure out how to do it, and post it up for you...
I know the story thus far has caused many of you to question this shop's integrity. I realize the belt size was a mistake, as was the comment on the non-existent knock sensor, apparently. However, I have been dealing with them for a few years, and I have seen a ton of the cars they have worked on and tuned, and talked to a lot of local guys who have used them. The last time I was in, the largest Ford dealer in town had his personal GT40 on their dyno for a pulley swap and tune. I have seen lots of very nice cars that they have worked on with extinsive mods, countless procharged, Maggie'd, and nitroused LS1's, Mustangs, Vipers, etc. I know this doesn't mean they are perfect, but they have been around and worked on a lot of cars, and seem to keep customers coming back...
When I asked over the phone the other day, he said it was a 74.5" Gates, but when I went in yesterday, he mentioned something about the old belt not being a Gates. Did he lie the first time, or mis-speak? I don't know. He specifically said the one they put on yesterday was a Gates. He commented that although it was only 1/2" smaller in length, it was a Gates, and considerably thicker than the 74.5" belt the car had on it before. I'll snap a pic tonight and post it up for confirmation...
I was reading up on the datalogging function on the SCT tuner, and it appears that I have to tell it what parameters to log. What would you like to see, and how should I drive the car? I presume idle for a short time, and then run it to redline in 2nd or 3rd gear?
The reason you're catching flak man is because we've seen countless threads were people come on here with issues from a local "well known" shop that has done all these car's has screwed their car up. Then after getting all kinds of advice from us they go back to this shop time and time again to continue getting screwed.
It doesn't matter how many "badass" car's they've done, could very well be that many of those cars have issues and don't know any better. That same issue has happened here locally as well, to quite a few cars that have some serious money in them. I've personally had issues with an extremely well known shop that has in fact tuned hundreds of Cobra's, but had I not followed up and datalogged and dynoed my car I would have never known how bad my tune was as it seemed to run pretty good. How many people go back behind their tuners and check their tune via datalogging and getting on another dyno to verify?
Log these parameters, and try to do a 3rd or 4th gear pull if you can safely.
Engine RPM
Coolant Temp
MAF counts
Inlet Air Temp
Downstream Air Temp (Charge temp or IAT2)
STFT
LTFT
Pressure Drop Across the Injectors
Fuel Pump Duty Cycle
Spark Advance
Battery Voltage
TPS counts or voltage
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I got everything set up on the SCT, but I couldn't find the pressure drop across the injectors. If you'd be so kind to tell me where that parameter is, I'll get a run in the morning. Also, I got all the other parameters set up, and idled the car for 30 seconds and saved the file. It saved as a CSV file. Is that the correct format? Would you like me to e-mail it to you for verification, or is there another way to post it up for you to verify? Thanks for your help.
I tried to shoot a pic in my garage tonight, but it's too dark to get a good shot, even with a flash. I'll try to get one tomorrow.
If you can't find that parameter try fuel rail pressure. Once you save it you can email it over or post the link, it should be saved as an excel file to be viewed as a spreadsheet.
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