vinceI

iTrader: (5)

I didn't look back to see if u mentioned these things but assuming the car has a 28 inch tire and mid 3 something gears and that the pull is in a trans gear that is 1 to 1 that thing is slipping bad. Its not even getting 130 Mph at 6800 rpms.

Forcefed86

iTrader: (4)

@ 118mph! Unless your running a 6.25 gear or something U have trans/converter issues for sure. What rear gear and tire height? What gear was the car in when dyno'd?

Suncoast Rod Shop

The pulls were done in 3rd gear. Don't know what the rear gear ratio is?? I know the rearend had been upgraded but neither myself or the owner knows the gearing. I'm guessing 3:23 or 3:42?? I'll have to measure tire height - they're 22" dia rims.
This run may have been the pull that the coupler at the throttle body / inlet tube blew under boost and he let off. I wasn't present when that happened ( left to go grab lunch)

Suncoast Rod Shop

I have to modify the pipe to the throttle body, get it back on, and we're going to try some higher octane fuel to bump up the timing and see what that results. I'll post those graphs along with A/F , timing

vinceI

iTrader: (5)

Coupler won't effect the slip if anything being down on power would help the looseness of the converter... Either the trans is slipping or the converter is way too loose. 3rd gear should be w to 1 so if the tires are in the 27 to 28 inch area your up at 20 % slip or more and you would want it down around 5 %. I would bet it would make the same power on 5 or 6 psi.

Forcefed86

iTrader: (4)

You need to know what gear is in the car.

http://www.how-to-build-hotrods.com/gear-ratio.html


Rim size doesn’t help us. We need the tire diameter. What does the tire say? 255/30 R-22 etc…

http://www.discounttire.com/dtcs/infoTireMath.do

Coupler wouldn’t matter. The MPH is WAY off. Honestly if your “tuner” didn’t see this I’d be looking for another shop. Not saying anything bad about his tuning ability, but I’d want a shop familiar with racing in general. Should throw up a red flag immediately when a 1000+hp car is at 118mph near redline. You should be at 160-170ish if you are geared properly IMO.

jtotheizzo

Boy this looks familiar ehh forcefed?

Don't live in denial like I did. Find out your rear gear/tire diameter and calculate your slippage for sure. The reason I have been fighting my issue for so long is I was sure I must have been doing something else wrong when the data was staring me right in the face.

I will regurgitate some advice forcefed gave me before. What are your trans temps and what does the fluid look like. If it's the Trans slipping you will know from that.

Suncoast Rod Shop

Good info - thank you!
When the tuner was doing light initial pulls at 7psi boost it was only around 500whp. I thought it seemed weird that at 14psi it was only making around 650whp.

Suncoast Rod Shop

I will check the trans fluid today when I stop back by. Really good information. This is why I ask. A lot of knowledgable folks on here willing to help/share info.
Btw - tire size is 295/30 - 22 which puts it at 29" tall

vinceI

iTrader: (5)

Your welcome. 500 at 7 seems pretty low too. I'm guessing the trans is slipping or the converter is hurt not just to loose. A 3.42 gear, 29 inch tire, going 130 mph at 6800 is 24% slip. That's were your problem is. You just need to figure out if its the trans or converter.

Suncoast Rod Shop

I just stopped by Nelson Competition and showed him the graphs and he's saying the same thing. He's leaning more towards the converter but agreeing all the same - trans/converter slippage. It's possible that when that first initial 800whp pull was done awhile back (several years ago) the trans/converter were fresh and during the time the car saw street use before I redid everything last year - it put a hurting on the trans/converter. That was one thing that wasn't pulled out of the car & addressed, just the engine, turbos & related components... Makes sense tho! You guys have been a big help on input. We'll get it addressed and re-dyno'd and fingers crossed puts down more respectable numbers. Been a long hard road for this car/ customer.

408GT

iTrader: (2)

I've been there done that with my 4L80. If it's been a few years since the 800 whp pull I'd definitely be suspect to the trans and converter. It doesn't take much to hurt a trans with 800+ whp in a big boat like this. I'd have someone go through the trans and get a good triple disc converter for it (Yank, Circle D, Jakes, etc.) Someone that knows 4L80's. Good luck with it, and keep us posted.

kingtal0n

iTrader: (1)

so basically 1. you have not verified the size of your injectors, and you are taking the word of some guy on the phone that they are the right size, and 2. you have no idea whether the fuel pressure is dropping or not.\

just saying its easier to check your fuel pressure and the number on the injector than it is to change a trans.

Heres a thought. At 15psi of boost, if your regulator was 45psi to begin with, and there is no reference, you will be at 30psi of fuel pressure, instead of 60. That could easily be your "missing" 500 horsepower worth of fuel.

98Camarod

iTrader: (43)

What kind of shift extension do you have at WOT?

Suncoast Rod Shop

It's not running lean. I never said I didn't know if the fuel pressure was dropping on this run. On the original 800whp pass yes. This is what it's doing for fuel right now - 125lb/hr. 62% X 8 = 620lb/hr. More than plenty of fuel for a 650 pass. Boost reference on the regulator is hooked up and working.

Suncoast Rod Shop

After I left the engine builder today I went back over to the Dyno/ tuners shop. We went back over the graphs more thorough with curser and saw where the converter /RPMs flashed to 4900 @ 50mph. Definitely a slippage issue. We didn't see this at first. I told y'all I'm dumb sometimes - lol!!

kingtal0n

iTrader: (1)

Im not saying the car is running lean, I am saying your pump output and or fuel pressure is the reason your engine looks like it is making 1000 horses when its only putting down anything less, the computer isn't telling you that the engine is using 125lb/hr- the computer is the idiot just shelling out a number based on assumption, it is completely wrong. You have to apply common sense, such as rwhp dyno output results compared to air fuel ratio. The computer has a fuel pressure assumption or injector size assumption. You seem to have a simple regulation or pump problem. Again, I am not saying you did not put enough thousands of dollars into the fuel system, I am not even saying you need a thousand dollar fuel system. We can all do 750 with $350 twin walbros in an OEM tank and get 30 to 50k miles out of that with a great efficiency. If plumbed correctly, that is, I mean you have to make sure the second pump output is nicely correlated with the first, that the other pump comes on only when it is needed, so we conserve many resources such as issues with the return (you want a tiny return when the second pump kicks on to make sure you put the squeeze on the pump without expensive regulators and expensive fuel lines, it is mainly the feed and how much pressure/application we want to run and how much risk at whatever kind of rail/system). You have some fuel system with a regulator that seems to be passing to much to the return, your fuel system is so good and the regulator is so huge and maybe a vacuum line is disconnected for good measure somewhere or insufficient (you DO have a dedicated vacuum source and not a heavily T'd line right?) This is just an example of how you use a proven design (a cookie cutter) if possible for repeatable, reliable results.

Also I am not saying the converter is any good, it could also be bad from age and use. The simple diagnosis is your $999 fuel system is returning more of the juice to the tank, its the simplest explanation, should be related to the computer output fuel number. the converter could be old and trans could be shot and all that too-, I would do a compression test and see 160+ even across the board, boost leak it, hit it, lock the converter up when you make the pass to eliminate all this question about converter slippage factoring in, and get a converter that can lockup at WOT (take some of that fuel system money) if you don't have one its practically an essential part of the fundamentals of automatics 101. Transmissions got a set of clutches in it, if you lock the converter clutch and the rpm correlates to wheel speed the way you expect, the clutches aint slipping and you arn't magically dissipating 400 horses. I am not sure how much a torque converter can inefficiently transfer in the case of wear or age, but I can imagine it can be abusive and related to the total output problem if not performing properly as indicated by the desired stall speed range. I don't think anyone calculated how much energy would need to be lost to the fluid to account for 100 horses either, so none of us knows exactly how much delta T (find the heat capacity and convert horses to joules I guess, pretty simply but I am lazy) that is, and if you can do it for 100 you can do it for 300 or 400 and see exactly how much temp rise to expect pretty quick based on how much you think you are losing.

alocker

iTrader: (10)

I'm curious about what the trans fluid looks/smells like.

Suncoast Rod Shop

Ok I see what you're saying now. Very interesting information!! So do you think instead of -10 return I should step it down to -8? I'll have to re-check where the vacuum line to the reference port on the regulator is. I do have a vibrant vacuum manifold screwed to the firewall that's feeding/supplying vacuum to assortment of things so if the vacuum is coming off that going to the regulator - you're saying it's not pulling appropriate vacuum and needs to be plumbed directly off the intake by itself?

Suncoast Rod Shop

I haven't gotten a chance to check that out yet. Good point! I will do so next time I stop by the tuners shop.