S/C upgrade questions?

cdhd2001 · January 3, 2003

I installed a powerdyne supercharger kit in my 2001 chevy 2500hd 6.0L/auto/4.10 in November 2002. I have installed (December 2002) a goodyear gator poly belt to fix the slippage problem (no more slipping!). I have also checked all my hose connections to make sure they are tight. My boost guage is tied into the vacuum line feeding the bypass valve (is this correct?). ???

Here is the problem: I cannot seem to read more than 4.5 lbs of boost at full throttle. The pressure builds nicely from 2k rpms, but from 4.5k rpms to 5.2k rpms (computer shifted redline) I see no higher than 4.5 lbs of boost. I have been looking a supercharger pulley sizes, and notice that the 3.12” dia. pulley (came with my kit) is rated for 6 psi car and 4 psi truck. Does this mean powerdyne gave me the wrong size pulley? If I bought the next size pulley (2.90” dia.) would I be messing up the tuning? What should I do?

If I decide to upgrade to the smaller pulley, what do I need to do to keep the tuning correct and prevent detonation?

Thanks!

Tjwong · January 7, 2003

Did you check with the Powerdyne people to see what they have to say? Make sure that you have the proper OD pulley for your application. When I first installed my Votech kit into may 95 Vette I also could not acheive anywhere close to the advertised boost levels. However my problems were due to a few things. One, I had a built 396 with huge AFR heads, different than stock cam, headers, three inch exhaust and second and most important I was at 6500' above sea level.

At that altitude atmospheric pressure is about 11.5 PSI, right there I have lost 3 PSI of natures boost! The other reason problem was that the belt was slipping. Vortech supplies a 6 rib serpentine belt for the Corvette kits. There was no way to get enough Hp into the blower to get their rated 6 PSI let alone the fact that I wanted upwards of 12 PSI.

Take your gauge, make sure its calibrated correctly. Try to get a decent gauge that reads 0 - 15 PSI. If at all possible have it tested. I have seen way to many El-Cheapo guages that can be as much as 2 PSI off when used in that range. My profession is in process controls, I deal with very high end process controls and instrumentation in Pulp and Paper so I see lots of guages and instruments that are not calibrated properly.

Once you have your hands on a known good gauge, take your truck out for another drive. Watch the gauge as boost increases. If it gets to that 4.5 PSI range and that it starts to bobble and then drop if, chances are your belt is slipping. And if thats the case, then going to a smaller pulley won't help, its just going to slip even more as you get near the blowers "efficiency" curve. At that point its going to take more Hp to drive it and if the belt is slipping it create the boost you want or its advertised boost levels.

If it develops just 4.5 and levels off, perhaps you have the wrong pulley. Again you would need to refer back to Powerdyne. Some companies like Vortech will void the warranty if the pulley is change so beware! If indeed that the belt is slipping, you maybe able to try another brand of belt. I have had good luck with the Good Year gator back serpentine belts. They seem to grip better.

As long as their hand held PCM programmer had a proper tune for their advertised boost levels and you don't exceed that. Getting to the advertised boost levels will not hurt anything.

My answer to my problem was a cogged belt. I engineered a cogged belt drive on a spare LT1 engine that I had. I used Auto cad to draw the pulleys and tensioners on cad and sent them to my machinist friend who cut them out of billet aluminum.

Thomas Wong

cdhd2001 · January 9, 2003

I am running a 113.0" Goodyear Gator poly-v belt. I have the belt tension set where the belt has less than 1/4" give at the longest span (the way I was taught to tighten them when all belts were v-belts). The belt shows no sign wear to indicate any kind of slippage.

Another question. My motor is stock except for the K&N air filter, Powerdyne supercharger, and Flowmaster 70 series BBII muffler (dual 2.5" in/out). I have read that when you make the motor flow better you loose some of your backpressure and therefore loose some of your boost. Would the Flowmaster have caused the 1.5 lbs reduction in boost (4.5 lbs instead of 6.0 lbs)? If so, the total cfm should still be the same, so am I still making the power of stock muffler and 6.0 lbs of boost? If not, would reducing the supercharger pulley size to make up for it be a good idea?

Thanks a million!!!

gandolphxx · January 10, 2003

I run TOG headers and cutouts and still get 7.2 boost on my Whipple - i don't think it is the exhaust that is the problem - really sounds like a pulley issue.

Tjwong · January 10, 2003

I doubt with the mods that you made would have little or any effect on boost. It's either the belt slipping or the pulley needs to be swapped for a smaller diameter pulley.

Now if you said that you had a motor with CNC ported heads, a larger cam and throttle body, then yes I would say that it would have a effect on boost. But then again if you make those kinds of mods you drastically change the VE (volumetric efficiency) of the engine. And any time you do that other changes has to be made as well for all the pieces to work together.

And that is the key to performance, meaning that all of your bolt on parts has to work together to get the increases you desire. If one just bolts on a lot of stuff like what a lot of kids do today with these rice burners, all you would have is a lot of bolt ons that don't do anything to enhance performance.

cdhd2001 · January 10, 2003

Thanks guys for all of the advice. I am going to order a new boost guage to make sure that is not the problem.

Another member mentioned something about changing the direction the bypass is connected. I noticed that vortech mounts theirs backwards from powerdyne. Will this affect anything?

I am really very pleased with the truck's performance. I did my first full throttle takeoff on wednesday (push the pedal to the floor and leave it there!). Both rear tires were spinning and the amount of smoke was tremendous. It ran thru first gear to redline, then the governer kicked in & it hiccupped. When I pulled my foot off then reapplied full throttle, the tires squealed and the truck lurched forward like a rocket! Anyway, first and last time I will do that. I think I reached the point ridiculus and insane take over.

Last question. Will water injection increase the performance any, or does it just keep the motor from detonating? Do remember I tow with the truck, and it will be seeing periods of continous sustained boost.

Thanks again!

gandolphxx · January 10, 2003

water injection is only going to help at the track - high boost and no intercooler. Normal towing won't kick in that much boost and shouldn't be a problem.

It appears that less than 6 lbs boost will do just fine with the LS1

Lee_klm · January 11, 2003

cdhd2001,,

I am looking at a SC for my 6 ltr as well. What Powerdyne pt# did you purchase. It sounds like you are pretty happy with the unit?

What must you do to run your truck w/o the SC? For example, if you are far from home and something goes wrong with the SC. Can you just install the stock belt and go again?

Thank you.

1BADZ71 · February 15, 2003

When I supercharged my Z71 5.3L I ran into the same dilemma. I was supposed to be running at 6lbs of boost and it would only read 4.5, 5 tops if I had the peddle stuffed pulling my trailer maybe. I called Dennis at Whipple and he asked me if I had an exhaust system on it and i told him i did. He told me that is the cause of the the loss in boost. The flow increase in the exhaust has reduced the amount of boost pressure. I would buy another size smaller pulley as I did to attain the extra 1.5psi you're missing. I did, and it put me to 6psi. Maybe your exhaust is doing the same.

bstewart · February 17, 2003

Hey 1BadZ21 I am only getting 4.5 lbs boost on my H2 also. Did you have to do any reprogramming of your pcm and what size pulley did you end up getting? Did you notice any difference in performance with the 1 1/2 lbs. increase in boost? Thanks for the info.

cdhd2001 · February 18, 2003

Well, I have done some more research on the subject. It appears that most of the powerdyne owners are seeing 1.5 lbs less boost than the kit was supposed to make.

Appears going one size smaller on the s/c pulley makes up the difference. Everyone that has went this route have not reported any ill effects. :thumb: I am going to order my 2.70" pulley this week. Tell you all later how it works.

1BADZ71 · February 18, 2003

bstewart,

I did put the smaller pulley on and it made up for the loss that was created by the exhaust (so whipple says). The pulley I got was a 1/4" smaller to make up for 1lb. It actually did that...1-1.5lbs. I would definitely go that route. I dont know what brand charger you have, but just tell them you need another pulley to increase boost 1-1.5lbs and they should have no problem. It will help for sure.

bstewart · February 19, 2003

1BADZ21,

Thanks for your reply!

I have the Whipple. I called Steve at Whipple today and he said that it is probably a valve and told me how to get to it and adjust it. He said that it is probably not closing all of the way and that there is an allen screw that adjusts the closing of it. I will pull it apart tonight and let you know if that is what it was.

gandolphxx · February 21, 2003

1BADZ21,
Thanks for your reply!

I have the Whipple. I called Steve at Whipple today and he said that it is probably a valve and told me how to get to it and adjust it. He said that it is probably not closing all of the way and that there is an allen screw that adjusts the closing of it. I will pull it apart tonight and let you know if that is what it was.

Be interested in the results and details on the valve location.

I have run across a couple of threads that have noted the decreased boost, and fixed it by going with a free flowing exhaust - I run a Magnaflow dual 3" in and dual 3" out - not much holding it back there - but I do run with cutouts at the track.

bstewart · February 21, 2003

1BADZ21,
Thanks for your reply!

I have the Whipple. I called Steve at Whipple today and he said that it is probably a valve and told me how to get to it and adjust it. He said that it is probably not closing all of the way and that there is an allen screw that adjusts the closing of it. I will pull it apart tonight and let you know if that is what it was.

Be interested in the results and details on the valve location.

I have run across a couple of threads that have noted the decreased boost, and fixed it by going with a free flowing exhaust - I run a Magnaflow dual 3" in and dual 3" out - not much holding it back there - but I do run with cutouts at the track.

The free flowing exhaust would actually have the effect of reducing the boost, i.e. less back pressure. I have not tackled the valve yet because it looks like I am going to have to take alot of time to get to it. I will have to take off the throttle body along with all of the plumbing. On my application it (the valve housing) is on the passenger side and has a large hose that is attached with hose clamps and another small hose that goes into it. It has 4 screws and you take that cover off and I believe that there is another access plate behind that to get to the valve. You blow into the valve and if it leaks you adjust the allen screw down to where it is air tight. Sounds like apita!

Steve did say that if this was the problem then going to a smaller pulley would not increase the boost because all of the pressure would escape through the valve, which makes sense.