Low Boost 347

[ka67_72]

How can I tell if a blower belt's slipping? I'm working on my first real customer car so I'm trying to get it right.

Here's how it arrived:
All forged 347
Trick Flow Heads 170cc runners, 61cc, 2.02/1.60
Trickflow Street Heat 75mm upper and lower intake
75mm TB
80mm MAF
50 lb injectors
a used Powerdyne BD-11, 12PSI pulley
Comp Nitrous cam .555/.570 http://www.compcams.com/Technical/Se...umber=35-556-8
Flowtech long headers
3" X pipe
Flowmasters
old piggy back computer
a disappointing 374 rwhp with 8 psi pulley

He wants 500 rwhp and suspected the computer.
I've installed and tuned an AEM computer to 12.7/1 A/F with an AEM uego gauge, installed water injection, and talked him into a boost gauge.

I haven't built a dyno yet so I'm tuning on the street. My only experience has been with turbos, but I was expecting the blower to peak at 9-10 psi with the better top end. As far as I know it was dyno'd without a boost gauge. My first time out it was only making 2 psi at 5000. With a short wrench I could easily turn the blower pulley so I replaced the belt. Now it's only making 5 psi at about 2500 and carries it through 6200. I'm still suspecting the belt because the idler's maxxed out, but I couldn't get a 1/2" shorter one on. I don't know if it's making more power now but it will light the tires at 70. He brought a vortech V-1 T, with chevy brackets, and we've talked about intercooling, if the powerdyne isn't enough. Any advice would be appreciated.

Thanks,
Kevin

[camcojb]

sounds like a belt slip issue, especially since those use a 6-rib belt. Procharger had a lower end model that had slip issues; they'd sell you a 12 psi pulley, but there was no chance of ever seeing it as the belt would slip first.


I am not familiar with Powerdyne but their BD10/11 blowers are not big power makers. I'm guessing he'll need a better blower to reach his goals.

Jody

[deuce_454]

belt i smost likely slipping... try and apply soem track-bite to the belt and see of things changes.. if not this rules out slippage.. also i fyou have an IR thermometer you will see belt temperature sky-rocket on the chassis dyno.. bit the trackbite is the quickest and cheapest check i know of

[ka67_72]

I don't have a dyno yet, but a short romp through the parking lot took the belt up 20 degrees F. I'm going to try to find a larger diameter idler pulley and get some track bite.

Thanks,
Kevin

[deuce_454]

Originally Posted by ka67_72

a larger diameter idler pulley

i take it the larger diameter idler pulley is to increase belt contact (either belt tension or contact angle) on the driven pulley... (that or the idler part ot the sentence was a typo..)

last resort is a cogged belt, which would be my next suggestion btw

[ka67_72]

The idler adjustment was maxxed out so the larger diameter idler is to increase tension and try to wrap the belt a little better. The car is pretty much useless traction wise so I've talked him into putting some southside or megabite suspension under it before I rack up a bunch of money trying to make more power. He's going to get some track bite for the belt and drive it for a while. If he wants more power after that, I'm first going to relocate the idler towards the supercharger. I was also thinking about cogged belts and drive pulleys. I was going to check with McMaster Carr. What do you recommend as a vendor for cogged drive parts? The owner asked me today if the computer would compensate for running 87 octane without the water injection. If it had a knock sensor it would, but I tuned it on 93 with water so more boost may not be a good idea for now.

Thanks,
Kevin

[3kidsnotime]

What CFM is your head unit rated at and what RPM. Also you say you cant get the shorter belt on, I have run into this alot with customers, how are you putting it on? you need to actually put it on the blower first then the crank if you need to bump the engine.

[ka67_72]

I could probably get the shorter one on that way. I just didn't know if I should try to force it. I just sent an e-mail to Powerdyne to try to get some flow info.

Thanks,
Kevin

[ka67_72]

He picked up the car on Saturday and is very happy with the improvements in drivability and power output. I never got a response from Powerdyne, but we're making just over six pounds now and according to the EMS using the calibration data I input from the MAF cal we're flowing 64 lb/min of air. I don't know a good way to estimate power from that. Except for the motor, a six point cage, and subframe connectors the car is stock and severely traction limited. We'll see if he comes back for more after he get's some traction.

Thanks,
Kevin

[AllSpeedAndy]

Glad to see customer happy...in some of our experiences with the ProCharger stuff, we have seen them pull the boost number on the dyno after some track bite treatment, then go for a real world drive and see considerably less boost on the street, but lots of spinning and sliding...So is it plauseble that with the spinning of the tires, the load on the engine is decreased as traction goes away causing the thing not to pull the boost as it was locked in and hooking on the dyno? Or should this cause a spike in boost presure?