Engine/Transmission (1994 - 1998) Twin questions

[JHastings]

Well, it is time for me to do my senior project for Cal Poly so I am pretty sure that I want to fab up a set of twins. My goal is a budget set of towing twins that I am hoping will cost less than a big single. Pretty sure I'll use my 35 over a HT3B, but am open to suggestions if you think others might be better i. e. S400... However, I still have a lot of questions in my mind and some might be some pretty dumb questions but here goes. How do I record drive pressure? Is there a guague I can make to record the backpressure? What kind of tubing should I make my hotpipe out of and how thick should my flanges be? Should I MIG it or TIG it? Also I was thinking about just milling my 12cm WG housing and putting in a big WG unstead of thie little stocker. I was hoping I could get around an external WG if possible. Also what kind of mileage do you guys with twins get? Same, less, more? What pitfalls did you guys run into with your twin projects that I could avoid? I am sure as my project progresses, I have a lot more questions so thanks in advance.

Jamie

 

[TNTNANCE]

I have a set of twins on my 97' and i am having problems with the head .

I do have o-ring and studs but that is not enough. Now I need to do fire rings.

so all I am tell you, is right the first time. Do fire rings and then you can put as much boost as you can handle.



97' 2500,twins,370 inj,ats ark flow,4k springs,13"clutch,water/meth,home made fuel plate and intake,5" exhaust, and big valve springs.

 

[BPonci]

A proper o-ring job will hold 60 to 70 psi just fine. You do however have to make sure the o-ring protrusion is correct and do your retorques properly.

 

[MrBee]

Some general thoughts

1. Make your flanges thick enough so they will not warp with the heat. If they do, you will have headache after headache trying to chase the leaks. Save yourself the grief and make them thick and if you know a machinist with a surface grinder he can make then very flat.

2. If you have a choice of MIG or TIG, I would use TIG. Both are very strong but it has been my personal experiance over the years that TIG has less failures on side by side identical parts,

3. Use good seamless tubing (maybe 4130 Chromoly) but most important is that the tubing is mandrel bent. That will insure that the flow will not have a bottleneck (area for heat buildup).

4. When laying out the path for your tubing remember that gentle bends are much better that sharp bends.



This post board has a wealth of knowlege and all I have contacted have bent over backwards to answer any question I have had.

Good luck!

 

[zstroken]

This is a project for Cal polytechnical institute??

 

[JHastings]

Perfect thanks for all the replies. I will probably start gathering stuff here in a bit. Yeah I go to California Polytechnic State University in San Luis Obispo "Cal Poly". What do you guys think about recording drive pressures? I need to make this a bit academic and so I am going to try and record as much data as possible as well as maybe putting this thing on the rollers before and after.

Jamie

 

[Forrest Nearing]

always watch drive pressure. it's an invaluable tuning tool IMO.



even on my single turbo truck, it's shown me when I had a boost leak, but with twins it's a great tool

 

[JHastings]

How do I measure drive pressure? Do I just put some form of a boost guage with steel lines on the exhuast side?

Here is what I was thinking for my setup, but am open to suggestions. Remember this is a total budget twin setup and is going to have to be absolutely streetable. It is my daily driver and 75% of all my miles are in town.



-My 35 with a 12cm wg housing, but put the ex housing on the mill and taking out the center divide as well as puting in a much larger wg. (I saw one guy put in a 40mm internal in his 12cm).



-All over a 3B with a couple of blowoff valves or at least bungs for blow off valves, should I need them. (Should I get a PDR 3B and how much are they?)

Thanks,

Jamie

 

[Forrest Nearing]

I would go with an external WG with a little 12cm turbine



plumb drive pressure just like a boost gauge... I used copper tubing from the exhaust manifold, about a 3" coil, then up across the cowl to the brake booster, then nylon from there

 

[Forrest Nearing]

also, I think once you get the popoff valves set up, you'll look for a different option when you watch drive pressure. hopefully not, but...

 

[JHastings]

Cool. That sounds good. The ex gas is cool enough by then to hook it up to a regular boost gague. Thanks.

What do you mean by I'll be looking at a different set up? Will my drive pressures be too high with blowoff valves and should I not even do them? One guy on cummins forum seemed to have good drive pressures, but then again his setup was pretty different. I don't know if he had blowoff valves or not.

here is the link to his twins, seems pretty cool, but I don't know all that much and am just learning, but seems that by keeping an internal gate, that is that much more ex gas to spool the 3B if you can keep drive pressures low enough. If I could get around using an external wg I would b/c aren't they pricey?



http://www.cumminsforum.com/forum/c...fabrication/1854-40mm-internal-wastegate.html



Thanks again for the input, I do appreciate it and I will probably be looking at this thread for awhile since this will be a big project for me and I will have a lot of questions and will need a lot of help.

Jamie

 

[JHastings]

I was looking at some prices today and at City Diesel anyways, a S400 is only a tiny bit more than their 3B. If it performs like people say they do, why go to a 3B instead of a B2 or S400. Is the only reason to go to a 3B is because they are cheaper or do they a better turbo for guys like me that just want a good set of Daily Driver twins. Does anybody know if city diesel mods their 3B's? I have heard that it is best to get one that has been modded a bit.

Jamie

 

[zstroken]

Perfect thanks for all the replies. I will probably start gathering stuff here in a bit. Yeah I go to California Polytechnic State University in San Luis Obispo "Cal Poly". What do you guys think about recording drive pressures? I need to make this a bit academic and so I am going to try and record as much data as possible as well as maybe putting this thing on the rollers before and after.

Jamie

That was why I was asking if it was "Cal Poly" I saw it some lattitude to be used to make it an academic project. Lots of fab work and all. You have it right take lots of data, present graphs, and should be good to go.

 

[JHastings]

No ideas of whether to go to a S400 instead of a 3B on a small set of twins? I am only going to push 350-450 hp through this thing. Is the only advantage to the 3B the price and does a s400 outperform it in all respects? Who mods HT3B's for faster spool and are they worth it?

Thanks,

Jamie

 

[RonA]

If you are looking to stay under 500hp I recommend neither one. I run a K31 as a primary and love it. It will outspool a 3b or large S400 by a good margin. The K31 runs a 71mm wheel an has a built in wastegate. They aren't cheap($900 or so) but are an excellent choice. I have run K31, 3b, S400, and S400-80mm. The K31 is the best daily driver I have tried.

 

[AFarmer]

Go for the B2/S400. You'll be glad that you did.

 

[JHastings]

The K-31 sounds really good, but unfortunately, it is way out of my price range. I am looking at $650 max for my big charger. If I do go to a B2, whose do I get and what size exhaust housing? thanks.

Jamie

 

[JHastings]

Looked at some other guys setups. Looks like all the guys running B2's have o-ringed their coldpipe and the guys that are running 3B's just put a rolled bead in their cold pipes, put a boot on them and call it good. Is it hard to o-ring the coldpipe? If it is I just might go with a 3B to keep stuff like that easy.



I am trying to keep the work load down as much as possible since this is a budget setup and although I can get around the shop and I have some good help, I am not really all that experienced.



So, whoes B3 should I use if I go that route? City Diesel, Htt... ? Also anybody got part #'s for a plane jane 3B witha 26cm housing? Also have been looking misc. parts from Rips Aoutomotive, but are there any others out there with good stuff?





Thanks,

Jamie

 

[JHastings]

Well,

Decided on the BHT3B with a 26cm. housing. I could not pass up the price. Also ordered all of the raw parts such as 90* mandrel bends flanges etc. from RIP at source automotive. He is very helpful and suggest him to anyone woh is undergoing a twins project. Going to start the build and machine the center divider out of my 12cm wg housing and enlarge the wg. Now all I need is a 90* hot pipe to weld to my two flanges. Is schedule 80 the recommended stuff or schedule 40?

Thanks,

Jamie

 

[RBrunson]

Sch. 80 is way too heavy. Sch. 40 is rated at 7000 psi bursting pressure. I don't think you will exceed that.