Engine/Transmission (1998.5 - 2002) Twin q's

[PetesonM]

Ok doing a lots of reading on twin set ups for my 99'. Want to run a hybrd 40 for the small. and ? for the big. this will be a home build. What i dont get is on all the setups that I have seen the big turbo looks like it is blowing through the small one. how do you control the drive pressure to the small turbo? how do you not blow that baby up or overdrive it? Do you do it by turbo size wastgates or fuel. thanks for replies.

 

[SRadke]

The S400 is a good turbo below the 35 hybrids. Not as cheap as a HT3B but spools a little faster.

The wastegate on the small charger will bypass more exhaust than it does in a single application so the top charger will not be working as hard.

-Scott

 

[DCreed]

in compounds the top charger should have a wastegate for both volutes as well as porting and increased travel and/or an external gate. The S400 can be had in many sizes from 65 to 80mm inducer and T4 and T6 ex housings the HT3B is 74 or 76 inducer and 22-32cm ex. housings. If you dont have studs/rings on the head stick with a smaller primary for low end boost and gate the top turbo early so total boost is under 50psi. 25 from the top and 25 from the bottom. Twins are more complicated than a single but also have greater benefits. but to run twins under 45 psi you may as well just run a single.

 

[fox]

I don't agree with your last statement!!!!

I tried several singles.

These twins spool like stock and i have seen 55. I did retorque the head bolts.

I can tow, race, what ever and don't need to stare at the pyro!

 

[DCreed]

I don't agree with your last statement!!!!

I tried several singles.

These twins spool like stock and i have seen 55. I did retorque the head bolts.

I can tow, race, what ever and don't need to stare at the pyro!

Fox, you currently have UNDER 450 RWHP. The S400 can do 55psi on its own. My statement was simply that twins have alot of options but most will need studs/rings to prevent failure over the 50psi they can easily make. the pyro is still an issue if he puts an S480/1. 55AR under the 35. I provided more specific info than just S400 as there are many options of that turbo that can make or break an otherwise good twin set. Fox, yours is prolly a 465/1. 10 AR, no?

 

[fox]

I don't know what the A/R is. It is all from Source, if that helps.

I have not ever dyno'd this truck. I know it doesn't work this way, ( as all the kids and amatures do it) but the Tst box is a comp=180, mach @'s are 105, smarty adds what?

I have refered to it as 475 hp.

What do you think it really puts down?? No challenges or offense wanted!!!!

 

[DCreed]

I don't know what the A/R is. It is all from Source, if that helps.

I have not ever dyno'd this truck. I know it doesn't work this way, ( as all the kids and amatures do it) but the Tst box is a comp=180, mach @'s are 105, smarty adds what?

I have refered to it as 475 hp.

What do you think it really puts down?? No challenges or offense wanted!!!!

No offense. I have run the smarty/tst/jammer 100s with a HTBG and put only 385 RWHP but I know I was lacking air and the VP was dying so rule of thumb is fuel less 20% with an auto 15% stick. So I figure 225 baseline (generous) +105 machs +180 tst +65 smarty = 475 - 20% = 380 RWHP auto and 404 RWHP stick. The twins should net an additional 10% so...

 

[PetesonM]

So you guys are sayn that if you are running twins I should budget for head studs or o-rings? What I am looking to avoid is lag with a bigger turbo. If I build this system and wastgate it proper, are twins worth it now. (remember the system is being built by me. tubing, oil lines ect) or do I put on my big turbo for now and live with the lag till I get head work and twins built?

 

[DCreed]

until you have the fuel to make big boost, the studs/rings can wait.

 

[SRadke]

... . but to run twins under 45 psi you may as well just run a single.

This is the part of that post that is incorrect. Twins, even if regulated to 45 psi (whether by fuel or wastegate) will spool faster and flow more air than a single. To do with a single what you do with twins you give up your ability to safely work the engine at low rpm. Towing is night and day better with twins rather than a single with regard to egt's.

 

[Forrest Nearing]

I don't agree with your last statement!!!!

I tried several singles.

These twins spool like stock and i have seen 55. I did retorque the head bolts.

I can tow, race, what ever and don't need to stare at the pyro!

horse pucky!



I've run a PDR35-12 on top of an S400 on my old 98 12v. the sps62 I replaced them with made 50psi about 500rpm earlier than the twins!



the EGT's were lower w/ the twins, but they were not uncontrolable with the sps62, and the truck was 10x quicker because the boost needle was like a throttle position readout... with the twins it looked like another tachmoeter



UNLESS YOU TOW HEAVY... if you don't need more than about 50psi, just put a nice single on it and enjoy quicker spool up

 

[Forrest Nearing]

This is the part of that post that is incorrect. Twins, even if regulated to 45 psi (whether by fuel or wastegate) will spool faster and flow more air than a single. To do with a single what you do with twins you give up your ability to safely work the engine at low rpm. Towing is night and day better with twins rather than a single with regard to egt's.

towing is night and day and the twins really shine... but a good single is going to hit 45psi way earlier than a common set of twins

 

[SRadke]

Twins built with a 35 will not spool up as fast as a single 35, this is true. But, twins built with a 35 will cool far better at a given boost pressure than a single 35.

 

[fox]

We all have our opinions and experience!!!

I tried, after the stock HY 35-9, a HX 35/12, then a PDR HX40/16, then to a SPS/14. From that to twins.

These twins have it all. Only down side is oil filter is harder to get to.

The hx-40 and SPS both were not towable for me, on my truck. They were better on the top end of course than the first turbos 's, but with the S-400 I have it all.



Heavy smoke too. Now -with the new smarty set-up, I have tuned ALL the smoke out.

Oh, I run with the box off most of the time, unless someone needs to play.

 

[Forrest Nearing]

I'm glad you like your setup... having an automatic helps because you don't fall out of boost, but I've had two manual transmission trucks with twins, and I hated them because I don't tow anything.



If you tow, nothing beats twins!!!!

 

[DCreed]

I have to agree with Forrest, for the average DD that tows light and is under 600hp and 50psi a single works fine and much simpler/cheaper and in most cases quicker to spool. But if you tow often or heavy, or are a HP junkie with over 600 RWHP (I do BOTH!) twins is really the only option.

 

[PetesonM]

So I guess I started something here. I want to end all this with a simple question. I want twins but with a car I am trying to finish and a need to fabricate I need to be responsible. my edge comp drag maxes out my turbo and my injectors need some love. so why not upgrade. I dont want to get into the head gasket. but also dont want the smoke and lag of a big turbo that is why i am leaning towards twins. so im taking the list advice on this one. My truck is a daily driver that plows in the winter and tows 70 percent of the summer I like to do some drag racing for giggles(3. 55gears). make your sugestion and I will take it from there thanks to all who have posted and all that will!

 

[Forrest Nearing]

you'll like them with the auto