Engine/Transmission (1998.5 - 2002) Twins & blow off valve

[V-Metalworx]

I think I'm finally ready to start building my twins my question is on an external waste gate anyone have an idea on what to run and why is it I can find them from $50 bucks all the way to $500 I also wanted to know if their is a way to adjust it from the cab I noticed on the ISB engine that Sheid used to display had some type of adjustable valve on it anyone have an idea what it is for my turbos I'm gonna start out with a stock hx35-12 on top the bottom will be a HTB3E with a 23cm housing I don't want to run much over 50to60psi I just built a new engine with a balanced bottom end 14mm head studs and a commetic mls gasket so I think the head will stay on it. another question on the blow off valve is the spring psi the highest spring I have found is a 14psi does that mean it pops off at that or what I plan on building a custom header for this and I will place the bov in it right before the turbo I dont know weather to plum the blow off tube to the hot pipe or in the down pipe any info will be helpfull thanks as always

 

[Huff N Puff]

Keep it simple,all you need is the waste gate on the HX35,depending on your fueling you shouldn't be able to make more than 65psi total.

 

[DCreed]

what will the EGTs and drive pressure be @50psi with a 12cm housing?

 

[V-Metalworx]

Keep it simple,all you need is the waste gate on the HX35,depending on your fueling you shouldn't be able to make more than 65psi total.

I've heard I can do that some one also told me I needed to bore out the waste gate hole in the exhaust housing to let morer air out I've made a ex flange for the HX and I thought abougt puting a hole in it and pipeing the waste gate strait into the down pipe instead of dumping it in the big turbo is their a way to adjust the stock waste gate to controll boost? the reason I wanted to run an externall gate was after I run it with the 3E on the bottom I would like to try to run an HT60 since I wont have to change the pipeing to swap them out I thought I would need the externall waste gate for the larger turbo will I'm fabricateing I would like to only do the work once.

 

[NoSeeUm]

You want to set them up so that the blow off valves normally do not open. Like you said their purpose is protect your HG.



By lifting the pop offs you are increasing drive pressure though. So it is better to use wastegates to control maximum boost. That is, if you run into that problem. IMO a better solution is to tune fueling so that really does not happen, even if it is with the right foot.



Are you installing a spacer between the HX35 and the exhaust manifold?



That seems to be reccommended as well. Read through the last issue of TDR magazine about single ported wastegates (HX35) and drive pressure. It is a good read. From my experimentation the drive pressure of a stock HX35 approaches 2:1 over boost at much over 20 psi of boost.



Jim

 

[Graphic man]

if your going to run NOS then a external waste gate is the way to go

 

[V-Metalworx]

You want to set them up so that the blow off valves normally do not open. Like you said their purpose is protect your HG.



By lifting the pop offs you are increasing drive pressure though. So it is better to use wastegates to control maximum boost. That is, if you run into that problem. IMO a better solution is to tune fueling so that really does not happen, even if it is with the right foot.



Are you installing a spacer between the HX35 and the exhaust manifold?



That seems to be reccommended as well. Read through the last issue of TDR magazine about single ported wastegates (HX35) and drive pressure. It is a good read. From my experimentation the drive pressure of a stock HX35 approaches 2:1 over boost at much over 20 psi of boost.



Jim

Iwont be running a spacer I'm going to build my own header whats the spacer for should I try to add tube length between the head and turbo

 

[V-Metalworx]

if your going to run NOS then a external waste gate is the way to go

not running NOS always kinda considerd that as cheating

only babies take bottles real men get blown

just kidding never really liked gas that much if others do thats fine

I don't like to have somthing like that that makes good power but you can,t use all the time and you have to worry abought running out.

 

[NoSeeUm]

Sounds like you pretty much have it handeled. Like I said, it is better to control boost with the waste gate. Controlling it with a pop off just makes drive pressure increase. On the other hand, speaking with PaulB, too much boost breaches a break over point where performance drops.



IE: Same boost + Higher drive = Lower Hp -and- Too much boost = Lower Hp



You thought about a external gate much?



I don't have one myself, but I can see the advantages. Especially if you are custom building your own twins. It really makes sense to go that way vice trying to jack around modifying the gate on a 12cm HX35.



Jim

 

[V-Metalworx]

Sounds like you pretty much have it handeled. Like I said, it is better to control boost with the waste gate. Controlling it with a pop off just makes drive pressure increase. On the other hand, speaking with PaulB, too much boost breaches a break over point where performance drops.



IE: Same boost + Higher drive = Lower Hp -and- Too much boost = Lower Hp



You thought about a external gate much?



I don't have one myself, but I can see the advantages. Especially if you are custom building your own twins. It really makes sense to go that way vice trying to jack around modifying the gate on a 12cm HX35.



Jim

Yes I've been thinking of an external waste gate thats kinda what I was meaning when I started this post instead of a blow off valve

I wanted to put the valve in the header right in front of the small turbo then run the dump pressure into the down pipe every twin set I've seen they always dump it right in the hot pipe into the large turbo I would think that would just keep pressure in the system am I wrong? I saw a setup Shied Diesel did one time and they had a external waste gate with some type of regulater in the line between the air horn and the waste gate I thought that would be cool then you would have a way to controll your pressure I've got pics of it if I can find them I'll try to put them on hear maybe someone could figure out what they used I tried to ask but I don't think they want to give out info unless they are doing the work I like how all this Diesel stuff is a big secret what type of twin setup are you running?

 

[NoSeeUm]

LOL



Pop off / external its close. I see while I was confusing you.



These from Olee Poole are the ones I stare (lust over) at every once in awhile.



Jim

 

[NoSeeUm]

I tried to ask but I don't think they want to give out info unless they are doing the work I like how all this Diesel stuff is a big secret what type of twin setup are you running?

The information is around and plentiful. Honestly, search around on the various diesel sites, there must be a bazillion "Building my own twin set" threads.



My twin set is a kit I bought from Rip Rook @ Source Automotive using a Dodgezilla 14 cm wg over an s400 (s475). He used to have many twin parts up on his website, but it has changed his website so much I can't find them these days. It used to be a really good place to look over flanges / supports etc... I bet Rip would still help you out with some of the parts you might need to buy, but I am not exactly sure what he is doing with twins these days.



Jim

 

[JR2]

All his stuff is still on the website, its just harder to find. He also sells it all on Ebay. . just search for it.

As for that set up in the picture. If I remember correctly they use the boost pressure to help hold the gate shut until the drive pressure overcomes it. I have a buddy with a set of twins that has a similar setup on it. They dump the excess drive pressure to the big turbo protect the little one... I like the set up they have as it has a LARGE dump, my buddies waste gate and dump are way smaller (like 1 inch od) and it does not work that well.

I am shopping for parts for twins myself (HX40 over HT3B), let me know if you find any smoking deals.

JR2

 

[NoSeeUm]

MVandever, no one really asked and you did not say. What is the target Hp you have in mind?



Jim

 

[V-Metalworx]

MVandever, no one really asked and you did not say. What is the target Hp you have in mind?



Jim

well I no this dosn't help but I really don't know I've got small injecters in it 125s and running a stock turbo and a comp box plan on doing more later the reason I wanted to build twins is I think they are cool and I can do all the fab work my self which I like to do and I can build this set cheaper than buying a good single I have all my flanges made all ready and have all the tubing for the hot pipe and down pipe all I need is some clamps and some hose and fittings and still need to fab the header not shure if I'm gonna run the turbo flange on an angle like factory and mount it upside down if I have enough room I might run the flange stait with the head to take some bend out of the exhaust flow so I guess the answer to your question is I'm gonna build it tune it till my rear end tells me it feels good then hit the dyno to se what it does :-laf

 

[V-Metalworx]

All his stuff is still on the website, its just harder to find. He also sells it all on Ebay. . just search for it.



As for that set up in the picture. If I remember correctly they use the boost pressure to help hold the gate shut until the drive pressure overcomes it. I have a buddy with a set of twins that has a similar setup on it. They dump the excess drive pressure to the big turbo protect the little one... I like the set up they have as it has a LARGE dump, my buddies waste gate and dump are way smaller (like 1 inch od) and it does not work that well.



I am shopping for parts for twins myself (HX40 over HT3B), let me know if you find any smoking deals.



JR2

I understand you dump the excess pressure out of the little turbo to protect it but if you dump it through the hot pipe into the big turbo won't that just spool the bigger turbo faster with more drive pressure and send it right back into the small turbo thats why I asked abought dumping it into the down pipe?

 

[DCreed]

I believe you're kinda right! but the exhaust housing on the primary is large enough to need that pressure to spool.

 

[V-Metalworx]

Thanks I did'nt know that the large charger I've got is only a 23cm I have heard people say that they were building to much bost with twins but I guess that would depend on your fuel so what do you do with excess pressure ?

 

[V-Metalworx]

All his stuff is still on the website, its just harder to find. He also sells it all on Ebay. . just search for it.



As for that set up in the picture. If I remember correctly they use the boost pressure to help hold the gate shut until the drive pressure overcomes it. I have a buddy with a set of twins that has a similar setup on it. They dump the excess drive pressure to the big turbo protect the little one... I like the set up they have as it has a LARGE dump, my buddies waste gate and dump are way smaller (like 1 inch od) and it does not work that well.



I am shopping for parts for twins myself (HX40 over HT3B), let me know if you find any smoking deals.



JR2

How do you like the HX40-16 as a single I will keep my eyes open for a 3B I shop on e-bay for used turbos but its kind of a crap shoot

 

[DCreed]

I would think if you've got enough fuel to overdrive the HT3B then you need larger twins like S300/400.