Engine/Transmission (1994 - 1998) Twin turbo set-up?

[DBR]

Well folks, went for my first test run this afternoon and here are some of the preliminary results. I can build boost at w. o. t. as follows: 30psi at 1500rpm, 40 psi at 2000 rpm and finially 48 psi at 3000 rpm. The 30 psi at 1500 is under heavy load going uphill in 5th. This is not something I want to do, as the drivetrane sounds like it's going to shudder into orbit. Low-end response is very good, still have some more adjusting to do and playing around with exhaust housings. I did tap the ehaust manifold to obtain a back pressure reading to help adjust the turbos. I think all the work was worth it!!

 

[Strick-9]

Wow, that's great news!



I really didn't expect you to have 30 psi at 1500 rpm.



Along with back pressure, tap the intermediate boost pipe to find the boost each turbo is making. That will help you decide which turbine housings to try next.



Congratulations.



You have given me a new desire to plunge into this twin turbo setup along side you. Now if only that UPS man will bring my ported head sometime soon, I can get to work on it!



How does it 'feel' on the top end? You know the feeling you got when you went to the HX40 from the HX35, it felt looser and freer on the top. Can you compare that feeling any?



-Chris

 

[DBR]

I do have a pressure tap point to verify boost between turbo's, I just need to install the tubing into the cab. To get the 30 psi at 1500 rpm, I have to really load up the engine, however it doesn't take much to get into the low 20's on a normal pull. As for the upper end feeling freer, I'm not sure. I have the stock governor springs installed and I don't have that much fueling into the truck. I plan on installing the 370 and governor spring kit again once I get the 60lb valve springs in. I also have a few custom fuel plates from Piers to play with. The present set-up for turbos is: 14cm Hx35 (Piers special) primary to 16cmHx40 secondary. I'll need to hook up the GN horse trailer and do some real comparison tests to see if I can sustain more than 32 psi before hitting 1300egt. Oh, forgot to mention that I never went above 1250 egt either, and that was against the governor.

 

[HoleshotHolset]

I think I speak for everyone when I say that I'm really glad that your setup is working well for you.

It's really encouraging to see all of your hard work come into a finished product that has exceeded even your own expectations.



Good job! Now sell me a setup... haha



Matt

 

[Roger rodbolt]

Great job!

DBR,



Kudos on the turbo setup, using what was available and being nice enough to share with us your engineering and results... that's great!! Thanks for keeping this forum ahead of the rest.

 

[400Magnum]

Congratulations!!!

Sounds like you have a sweet setup there DBR, Congratulations on your success!! It's always so cool to have something that you work on and sweat over to work so well in the end. It makes all the bruised knuckles and head-scratching worth it!

 

[DieselPuff]

DBR?

DBR,

I am considering the same project you worked on. I have the stock HX35-12cm2 and a HX40-16cm2 turbo. Have you been able to test this combo yet? Please give some more feedback to the performance, as I am very interested in doing what you did. Thanks



PS: I haven't seen Eric McBride post here in a long time. Doesn't he have a sweet twin turbo set up too? If someone knows what his turbo combo is, please reply.

Thanks



Michael

 

[DBR]

Things are looking good!

Well, I have some preliminary numbers, but haven’t been able to “really” test the set-up yet. Before doing so, I need to do a few things.



To start, I need to obtain an air filter before going any further with test-drives. I originally planned on installing the BHAF Napa 2790, but my local dealer wanted $55 for it (too much money in my book for a throw-away filter). So I decided to order a KN-0880 a few days ago from Jeg’s, $56. 19 to my door, far better than the BHAF. I still believe I can use the stock filter housing with a redesign to the cold side piping, I just hate to cut up perfectly functional piping.



Secondly, I need to let my replacement clutch seat before adding any additional power. The new design SBC clutch is a very nice improvement over the old one. Engagement is far better. I’m looking forward to putting this clutch through the paces.



My base lines before the twin set-up are as follows:

TST # 11 plate.

192 delivery valves

300 marine injectors

Stock governor and AFC spring.

16HX35 (Piers Turbo)

4” exhaust.

Peak boost 40 psi, max egts 1400 (against governor)



To date, with the few runs around the county test roads I use, this is what I have observed with the twin set-up. I have made no fueling adjustments.

3 psi of boost at 1000 rpm

30 psi of boost at 1500 rpm

48 psi of boost at 3000 rpm with a peak of 72 psi of backpressure and roughly 1280 max egts, this was against the governor. The only smoke I observed was against the governor, other than that it’s pretty clean.



I was able to reduce the peak backpressure psi to 68 by adjusting the primary waste gate to a lower value without affecting the peak boost value. I’m not sure if that would actually make a change on the peak backpressure values, however that’s what I observed. I’m still debating those results.



From what I have observed so far, this set-up looks very promising for towing and low rpm grunt, but with the 68/72 peak backpressure reading I wouldn’t try to go for real big horse power numbers. For that you would want to look at what HVAC is running.



Once I receive the KN-0880, hopefully Friday, I’ll start doing some better testing and be able to provide some concrete numbers to compare against the base line. Then I’ll change injectors to the 370’s and start playing around with fuel plates. I have a couple from Piers that look pretty promising. I might even install the governor spring kit again, I just need to finish installing the 60lb springs on the intake side.

What ever happened to Sport Bike? He was one of the first I remember who was fabricating a homemade system. Actually, he was the one who’s efforts inspired me to fabricate my own.



The funny thing is, I am already thinking about using some different turbos, but that’s only in the day dreaming stage.

 

[Garry Verheyden]

Why isn't anyone intercooling between the two turbo's? These set ups you guys have look great, and obviously work better than any single turbo, but I heard that if you get too much heat between the two turbo's (300+ degrees) you can make the aluminum compressor fins brittle. This could be a grenade waiting to explode and then there goes two turbo's. I don't know much, but definately want to learn more about this stuff. I can't afford to buy a twin set up, but I will be building my own system in the next couple of months. I know it will involve a heck of a lot more plumbing, but I am going to try to build a set up where the lower turbo goes through the main intercooler into the secondary turbo, then somehow intercool it again before it goes into the engine. If it works, I'll post the pictures so other people can see it.

Any opinions on this would be appreciated .

Garry.

 

[DBR]

Just a top and bottom view of the present install. I have been changing fuel plates and injectors with some very interesting results. I did hit 50 psi with only 1000 egt. I'm having trouble with this one? I'll ponder on this one for a while before getting in depth.

 

[DBR]

second view

 

[DieselPuff]

Thanks DBR for the updates. Are you still using the 14cm2 and 16cm2 housings? I only have a 12cm2 for the HX35 and a 16cm2 for the HX40. Do you feel like the small housings are limiting the top end performance from 2500 to 3000 RPM? Thanks again for the update. Oh, which parts when fabricating the twins did you have to actually use a mill or lathe? Thanks.



Michael

 

[HVAC]

I haven't needed a mill or a lathe for the three sets of twins I've built. You will need a way to cut the 4" fittings cleanly, either a chop saw or a power hack saw. You will deffinately need a welder.



DBR, it is sorta common to find your egt drop once the boost hits new highs as a result of the twin chargers. Would you say 50 psi is better then your current combo would yield before the twins?

Seems you will see some heat as the chargers gain momentum, then the egt will slide back down.

 

[DieselPuff]

Thanks HVAC for the info. If you didn't machine anything, did you make all of your parts from exhaust pipes (4" & 5")? Are you supporting your turbo with additional hardware? Any info would be appreciated. Thanks.

 

[HoleshotHolset]

DBR, nice results!

Keep up the good work and keep us posted... .



Mine are on order...



Matt

 

[DBR]

Hvac



I agree about additional boost, that's not what is bugging me. I pulled the 300 hp injectors and installed the 215s. I also pulled the #11 plate and installed one of Piers' custom plates. With the new set up, I was able to pull more boost. I actually let off the throttle when I hit 50 psi (gauge limit). What is confusing me is that I installed smaller injectors with a larger fuel plate which resulted in lower egt and more boost. I'm just not sure what happened. I would have thought that the 300s would flow fuel more efficiently than the 215s. The ability to make more boost with less egt confuses me. Power by the seat of the pants seemed to be equal (not a very accurate way of gauging). I have installed another fuel plate from Piers which fuels less and I'm seeing 44# of boost and no more than 1000 on the egt. These results I understand. I'm going to give Piers a call today and see what he has to say. The 300s and 370s have worked very nicely for me on a single turbo, better than the 215's ever did, especially when hooked up to a hx40. I'm just not sure if I'm seeing the big picture.



Dieselpuff



I used a mill to dress-out the exhaust flange to the secondary turbo and a lathe to fabricate the V clamp side to attach to the exhaust outlet of the primary turbo. I also used the lathe to fabricate the outlet side of the secondary turbo. This allowed me to use a v clamp to attach to the outlet of the cold side piping of the secondary turbo. There are pictures in the early part of this post.



There is nothing a good shade tree mechanic with access to a basic shop couldn't complete. There was nothing complicated in my install by any means. The only modifications I had to make to the truck was to weld out the oil return line to the oil pan. Other than that, no other cutting on the truck was necessary. I fabricated and welded out all pieces myself (however I did get a crash course in "lathe operation 101" from a good friend of mine at work), so that should tell you how easy it was overall.



I believe that on HVAC's secondary turbo, the charge air doesn't have a mechanical seal like the hx 35/40s. I believe you just use a 3" boost hose and clamp. HAVAC will need to answer those questions regarding his system. Remember HVAC is going for very high horsepower numbers (very successfully I might add) for drag racing, where I'm going for strictly low-end torque and egt control for towing. I don't intend on pulling hard on the engine much above 2500, 2600 rpm.



I have looked into opening up the waste gate orifice in the turbo's exhaust housing a bit to help with back pressure, I need to get more base lines before going that way.



One last thing to remember, I only chose to use these turbos as I already had them on the shelf collecting dust and wanted to see if and how they would work! I'm not sure I would go out and buy them to make a set-up, I would imagine HVACs approach would be better.

 

[DieselPuff]

Thanks DBR for the detailed reply. Are you still using the same exhaust housings (14 & 16)? I am thinking maybe the HX35-12 and HX40-18 may be a good combo. Have you considered trying that?



I, too, am using my existing turbos because my wife has me on a limited budget (she wants a new car ).



I am starting this project tonight after work. Thanks again for all the support.

 

[DBR]

Dieselpuff, I'm using the 14hx35 and 16hx35. I'm thinking of trying the non waste gated 16 for the 35 and 18 for the 40 for fun. I would like to get the back pressure down some. E-mail if you would like some further details on how to fabricate the exhaust manifold.

 

[BPINE]

Hey DBR, Your set up is looking good. Just a quick question on noise, how much turbo whine do you have compared to a single. All though Nowel's set up works well is is pretty loud and I'm not sure it would be good for the long hall with the family and the RV. I am still working with a single HX-40 for the time being and so far it is working well with the MY6 housing set up. All I have to do now is get the waste gate set up better because I don't think it will live long at 50 psi.

 

[HVAC]

Noise Level

Folks, don't let BPine's concern worry you much. He is the unsolicited receiver of my frequent high speed strafing runs and consequently we have shattered a couple of his windows!!! Point is, the truck sounds like a fighter jet from the right lane8)! I feel the turbo music is rather pleasant from within the cockpit Gets the ol' bladder pumping you might say



One thing is for certain, my opinion is totally useless since I'm now deaf (kidding)