Hi guys. I currently have the s trim off of my car and was comparing it to another s trim head unit that i recently got. On my s trim that was purchased back in 1998, the air inlet of the blower is about 1/4" larger then the other unit(3.75 vs 3.50). It's like this thing is a t trim almost. It has the race m bearings and the larger inlet. I'm going to call vortech tommorrow and see what they say about the unit.

I'm seeing about 10 lbs of boost on my car and about 500 hp. I'd imagine I should be seeing much more if it really was a t trim.

I was looking at the impellers of 3 vortechs (I know it's like they grow on trees here at my house); 2 s trims and a t trim. I can't tell the impellers apart enough to identify whether or not the s trim off my vette looks similar to my t trim impeller off my mustang.

 

I called vortech and they said that I probably have a t trim. I can't believe that I can't get more boost out of this thing!

 

If you're not happy with it, I'll take it

 

They should be able to tell you exactly what trim it is based off the serial number on the head unit, right? They used to keep records for those things

 

I called and they said that they only have the records for the newer stuff. Mine was from 1998, so they didn't have the ability to go back that far.

 

I can tell you that a T trim in a C4 LTx car will max out at a bit over 620 RWHP. That is about the limit to the blower. Its only rated at 800 or 850 HP. Once you consider driveline losses, and the amount of power required to drive it to that level which I beleive at around 100hp, you will see that its about done at the level. Glens car made 620RWHP, figure a conservative 15% drive train loss and 100hp for parasitic lose you get 193 hp in losses alone. Add that to 620 and you get 813HP at the crank. If we had turbos on the car, I would get much more than 620 to the wheels, but that is because I am using a waste product to drive the blower rather than the crankshaft.

There are other deciding factors as to why you are not making more boost that 10 psi. Factors such as inlet restriction which these types of blowers are very sensitive to. A large cam and very free flowing heads will also affect it. You don't want a large cam with a lot of overlap with a blower setup, at least not on the street. You don't want to be using the blower as a leaf blower that is venting out boost during the cams overlap period. Or you may have belt slippage issues. I got about 12 psi out of Glens car, I wanted 14 but it just wouldn't get there. And with his I really doubt that the belt is slipping, not with Gregs 8 rib and as much belt wrap as I had on it.

 

thanks for the input tj. I know that the t trim is capable of much, much more than I'm putting down. I do have decent heads (cnc'd lt4's) with all the supporting mods. I do have a gm hot cam which I am sure isn't ideal considering todays blower cams. The most boost that I've seen out of the car is about 11 psi for a fraction of a second. I would see roughly the same amount of boost 10 psi with 6 rib before I switched to 7 rib so I'm not sure that going 8 rib would really help me that much. I really think that itshould be making more power. I'm probably going to pick up a wideband and get more serious about dialing this thing in.

 

Russ,

One of the biggest differences between the stock vortech bracket and the 8 rib Greg is offering is the belt wrap. The extra idler helps tremendously.

With my old stock block LT1 I was seeing consistant 12 pounds of boost at about 5500 rpms.

Using the same setup with the 396 and 210 AFR heads and moderate cam, I'm lucky to see 10 pounds of boost on a good day ( consistant 9's) So this supports what TJ was saying that the parasitic losses and cam profiles inlets make a big difference. Im not sure how much the Rhodes lifters tone down the duration at idle, but your cam sounds dramatically rougher than mine does. It could be you are just blowing the boost through the overlap of the cam.

There is no comparison that the 396 is twice the animal the 350 was... I am running out of what the supercharger will support, as well.

hope this helps...

Mo