dodge24

Hey guys, thanks for the info so far! Turbolvr, my turbo is only a few months old and I thought the wategate problem only affected the older units. Mike, I am running 4.10 gears in my truck and it always seems that I am revving too much or starting to lug it. Do you think a different gear set is in order? I'd hate to go to tall and lose my low end torque off the line. As for power goals, I would like to hit a very clean 500hp.

Mike Holmen

turbolvr, my local turbo shop even had the hi flow TI compressor wheels for the K-31 that extend the compressor's operating flow map and its characteristic. I never asked about price. The next time I'm down there I get a part number for ya. The K-31 has an internal gate. My last GT4202/1.01 had a 42mm internal gate as well. My S475 doesn't have any gate. I would like to try a S480, but I don't like spending too much money these days. I have a garrett T-88 sitting on the shelf, but I don't have enough fuel for that bad boy.

dodge24, 4:10 are really meant for guys that tow heavy lots. My truck has 3.54 gears and triple disk 1800rpm hi stall converter. You could always just put on bigger tires.

kantdrive55

You have to be very VERY careful with an external gate. When you dump the secondary chargers boost the primary charger has to work way to hard to make up the difference and can overspeed and blow up.

Mike Holmen

Kantdrive55, what??? Over speed the primary? What??? How big is the wastegate? I want to see that. Most of us have issues with getting the primary to load up. Tuning twins are tricky stuff, I guess. I never had that issue. I think that your talking about the secondary, but you have to set-up the twins right and put a decent load onto each turbo. At the end of the day you only have so much energy available in the fuel, and the trick is to get all the fuel to burn.

I can only see your point if your running a truck thats running tons of boost, maybe, but then you have undersized the primary turbo to start with. Most of the time the undersized turbo will just run in the choke area at that point. Most turbos can run till 40-50 psi (depending on compressor map, thats around 3.5:1 comp ratio), then you run another turbo on top of that pushing another 3:1. thats close to 80-100 psi of boost. Most street guys aren't doing that. If you're running that much boost just slam in a bigger primary (more mass flow).

kantdrive55

When you see people with twins that have a charger failure 95% of the time it is the primary(big charger) When they open the gate on the secondary to help the primary then the overspeed and blow. I will look for the thread where our turbo engineer when through great extent to explain it.

Mike Holmen

I can only see that if you run an extra large gate, and total bypass the secondary but usally the secondary will see the incoming air first, typically surge causes the shaft to snap on overspeed. Usually my secondary stalls first and the stall would have to occur in the air tube between the secondary and primary. Thats my take, anyways.

TURBOLVR

I really dont see a 75mm S4 based size charger overspeeding on a little 5.9 . unless you are pulling over 800hp and/or running NOS there is no "hit" to the primary. I could see it with the little 57/366 towing set but not a 66/480 like mine.

Mike Holmen

I would like a ride in the truck that does break a shaft on a set of twins. I haven't done that yet, just burnt out a few. Seen a few broke, most are singles, running NOS and looking for more fuel.