JAyers

Heres the deal, Ive got a HT4B sitting on the shop floor. It came off a 855 big cam Cummins. 81mm compressor inducer, 88mm turbine??? ICRC. Anyways its got a 32cm single entry T6 exhaust housing, ive been told by several ppl that it will be alil on the big side but will work just fine. I need your alls opinion tho. Im thinking that my manifold charger will light quicker (less drive pressure) and due to the large exhaust housing, the truck will breathe alot better on the top end? Am I thinking correctly? Has anyone one ran one of these antiques? O and my manifold charger is a SPS62 with alittle wastegate/porting work done. Any input is greatly appriciated! Thanks!

Tate

Thats a lot of charger, considering guys running 800+ are using 80mm inducer compressors. It's gonna be real lazy on the bottom end. 1-5-3-6-2-4 ran an HX40 and HT4C combo, and he changed it to an HT3B instead. I'd look at doing the same unless you are looking for rediculously high horse power.

Keep in mind, though, I am no twin turbo expert.

JAyers

An HT4C is a little bit bigger then a 4B. I think its like an 88mm compressor. Im gonna call around today and see if I can find a smaller exhaust housing for it. Thanks.

Mike Holmen

You would need more fuel to get that turbo to lite right. As Tate said, its gonna be lazy slug without more fuel or exhaust flow (bigger engine). Wow that turbine housing is a monster and I bet that the compressor housing is larger as well. Can you find a smaller A/R housing for both the turbine and compressor? BTH-3B are pretty cheap and the same goes for the S400 turbos. You'll be maxed on rpms waiting for that turbo to lite up.

JAyers

Well ive got about $100 in it. It came off a Recon engine with about 40k on it, the block had acouple holes in it. I havent had a chance to call CDS and see if i can get a smaller exhaust housing. Ill have about 700hp worth of fuel pushing through the VE. And I doubt it will be enough.

Mike Holmen

What you running for the secondary turbo? The S300? You'll have to get the wastegate to work as you'll find that there will be some choking of the exhaust flow. I would set the wastegate lower than stock, around 26 to 28 psi. If the secondary wastegate flapper is large enough it should start to lite the 4C. If you go with stock waste gate, the primary will not lite very hard.

RonA

If you have 700hp worth of fuel you should be fine.I just went from an 80mm primary to an 88mm and spoolup was about the same. I have a smaller exhaust housing though.

JAyers

Mike Holman, yea im using the S300 as my secondary charger. I have a little port work done to the exhaust housing but the wastegate flappers are stock from II. Do i need to do any modifications to them? Or will just letting them open up early like you said be enough?

RonA, what size housing are you running?

RonA

1.08 a.r. exhaust.

JAyers

Thats fairly tight, wonder what that equates to in cm^3? What r u running for your manifold charger? Whats your opinion on the wastgate situation? External? Thanks for everybodys opinions and time!

Mike Holmen

You'll have to find the sweet spot to open the wastegate. I never built a twin S300 set-up. From reading here on the net, the wategate uses a spring and seem to influnced by the drive pressure more so than the Holset or garrett. I have my garrett set to open at 26 psi. I've run it closed and varied the pressure down a little as 18 psi. 18 psi worked really nice, but it was difficult to keep the wategate closed enough to provide a seal to provide decent spool-ups. I would go up one size of the S300 turbine housing (A/R ratio) than when you drive as a single. You have any info in the compressor and compressor A/R housing sizing? Just from reading the current info, the 4C isn't gonna be real responsive. Without seeing the turbo, I go by that most of the 4C came off large frame engines (800+ CID), lots of exhaust flow. They have large turbine wheels and large a/r ratios, then have smallish compressor impellers with large A/R ratio housings. For racing or sled pulling it should work. For street driving, the BTH-3B and S400 impellers are around the mid 70mm for inducer size and the compressor A/R ratio slightly up from what we typically run as a single. I just have built a few set-ups and go with I know that works well. Try out that twins set-up and get back to us. If you don't like just find another primary turbo and try it again.

RonA

I'm running a 64/71/16ss on top. I made 711 with this top charger and an S400 with an 83mm turbine/1.1 exhaust/75 comp. It did not need an external gate for the primary( I thought it would, so i put one in). This 1.08 might. The turbine wheel measures about 94mm but when it starts making boost it comes up quicker than I expected. I left room for one, but I was hoping I wouldn't need it.

JAyers

The s300 has a .80ar exhaust housing, im not sure about the ar on the compressor side. Industrial grinds the compressor housings smooth. Its a 62/71/.80ar. The 4B came off a 855 big cam cummins. Ive got it hangin off my spare engine right now. The hotpipe is all jigged up, ill finish it up within the next couple month's. Im a college student so time for this kinda stuff is slim to none. O and it is just a dyno queen/drag truck. So alil lag is ok.

JAyers

RonA, looks good, im hanging mine alittle higher and more over towards the fender. Ill get some pics up when I get time.