Timinva

To those running twins how much work do have your large turbo do? I run about 65 psi total at the air horn and the big turbo starts to build boost at about 20psi in the air horn. At 50 psi the big turbo is making 25psi. At 65 total the big turbo is at 40 psi, It seems that the longer I let it spool the more the big turbo works but I cant hold it wide open long enough to see just how much boost it can build in the ht3. Do these numbers seem about right? Also how much boost do you lose through the intercooler, it is more than I thought. Thanks in advance, Tim

Jim Fulmer

Tim how are your Twins setup, does your exhaust from the yop turbo just dump into the big one or so you have some sort of divorced wastegate. Also what turbo's are you using and are they off the shelf versions.

Jim

Don M

Tim,

I assume you have a boost gauge between the stages?

If so, can you detail how you have the boost gauge fitting installed?

In other words what is the type of fittings used in the pipe?

Currently your small turbo is only making about 4 psi. If what is happening that I think is.

Also, can you tell me about your twins one more time...I know you have the 3B ( is it a garrett?) and the top turbo I cant remember.

Don~

Timinva

I run a hx35/12 top and a ht3b lower with a 42mm wastegate dumping between the turbine housings. I drilled a 1/8" hole in the crosstube and mig welded a 1/8 npt fitting for the the boost gauge, also did it on the inlet pipe near the intercooler. I just install a temp gauge while testing and cap them off normally. Just did some testing and at 62 psi total boost the big turbo was making 35 psi. Also should 60+ psi boost keep >500hp cool? It will still get to 1500 without side temps at 58 degrees. Thanks guys Tim

Jim Fulmer

12cm is like a choke hold, if you have to run a wastegate housing try to find a bigger one.

Jim

Don M

Ok, At your peak boost of 62 PSI your small turbo is making about 4 PSI still. Im assuming your close to sea level or at least in the 500 ft elevation range or less.

The wastegate is doing its job of bleeding away plenty of pressure that drives the small turbine. A good thing, but the large turbo is still working just a tad too hard. You cant slow the large turbo down at WOT with your set-up at peak boost as built. Any more boost and your head gasket is at risk since its still stock, without an o-ring in the proper place.

Running more gas through the small turbine with wastegate adjustments might slow the big charger down some, but I dont think much.

The gas that is leaving the small turbine has expanded and cooled some as it enters the pipe heading to the 3B. At the same time the gas that is by-passed with the wastegate is hotter and more violent. Some thought and adjustment in this area could help your slight overboost on the big charger.

60 PSI is not enough to keep temps under control without ported exhaust runners, ATS manifold, and a good camshaft.

These things would relieve some of the EGT. Perhaps 200 degrees.

At peak boost here is the changes the small turbo will make in its boost level.

At 70 PSI it will be making 6 PSI
At 75 PSI it will be making 7.5 PSI.

Don~

Timinva

Don, I am at sea level and already run an ats manifold. What do you feel the big turbo should be putting out at 65 psi of manifold boost? If I shut down on the wastegate to divert more gas through the hx35 the total boost goes up also. Realize I need to o ring or fire ring the head, problem is having the tooling done, no diesel shops close and cant justify buying the tools for one use. Maybe a replacement head with the o ring work done. Are your heads ready yet? Also would going to a 26cm ht3 housing slow the big turbo enough? I am running a 22cm now. Thinking of doing that next and maybe a 14 cm housing on the 35. Jim, both turbos are off the shelf, what size small housing are you running and are you running a external wastegate? Thanks Don & Jim for the replies, keep them coming. Tim

Proram

8) If i can input my .02 w/out getting stomped. first get rid of the 12cm housing its killing ya. 2nd if i read right you run 4" ? is that the outlet size of the HT? or w/ a reducer.if it's reduced go to 5" the amount of air your flowing WILL be choked by 4" I run (ran) an hx 35/16 into a stock ht w/ a diveorced gate dumping into the head of the ht and Full 5"
also ran Bully Dog 8's, a drag comp, o-ringed and studded
and made 580/1070 and needed more air. and NEVER saw 1500 on a HARD pull, so it can be done. (with a little work)

Ok don , your turn to pound me,, Scott

Don M

A larger turbine housing on the 3B is a good idea to slow it some. It may still creep up some on you at WOT. Probably not though. I only have tuning data with the 3B from one truck. The 26 housing was used. The total boost from the 3B was less than 35. At 656 corrected HP. Uncorrected was 607 @ 2900 ft of altitude. At this elevation the turbines are really spinning hard to make the same pressure. Too bad they whip the air so hard it heats up pretty high.

I dont think you will have much if any additional lag. The small turbo is still taking care of that for you now. I would guess it probably makes over 15 PSI at some point before the wastegate takes over and slows the turbine speed.

I good way to find out is to continue to test the boost coming from the 3B and note the levels at the same time the manifold level is watched. It may take two poeple or tell-tale gauges.

I am currently doing a cylinder head for a guy in NY. He plans on big power. I dont use an o-ringing tool like others. I use a mill and cut the grooves to extreme accuracy. Porting is currently done by hand. I dont use the traditional flow equipment either. Traditional flow equipment is for engines that are normally aspirated. The 28 inches of water columb that is used is a vacuum. Smokey Yunick developed the standard back in the 60's for the 28 inches that mimics an engine that sucks in an air/fuel charge. Porting a head for a turbocharged engine that is using pressure to operate and not vacuum requires a different technology altogether. I finally have a handle on that 8)

Yes, I can do a cylinder head for you.

I do respectfully disagree that the 12 CM housing is a choke on your engine after the boost comes up. If the small turbo is making 4 PSI at WOT the turbine is not seeing much exhaust gas. Its mostly being by-passed through the wastegate around the turbine section of the small turbo. If you were making real big boost numbers and the 3B was still making 35 PSI I would get nervous. Of course you could and probably should try a larger housing to see if things improve, but with 4PSI from the 35 I would not get in a hurry.

Don~

Timinva

Scott, My ht3 outlet and downpipe is 5", I reduce it to 4". I reduce it to 4" about 6" past the bellhousing. I didnt think 5" would be required but will look into getting some 5" tailpipe. Did you run the 26cm housing on your ht3b? Thanks Tim

Timinva

Don, the best I can tell the ht3 starts making boost at about 20psi in the air horn. I need another eye, my gauges are 0-100 at the air horn and 0-60 at the cross pipe and trying to watch both gauges and the road is fun, especially when the ht3 comes on. I will get a 26 housing, I will have to pull the tranny cooler off the block because the 22cm barely fits with it on. When you get a chance pm the specifics on a ported o ring head. Then we will probably need more fuel {mach5s} especially if we can diminsh the smoke. Tim

Jim Fulmer

Jim, both turbos are off the shelf, what size small housing are you running and are you running a external wastegate?

Small housing is an 18.5 but I built mine with a non-wastegated housing, started with a 16 then to an 18.5 and a 26 on the 3B, but heck I'm just an average 700 hp guy my combo doesn't work perfect.....wait it's not mine now....it's sold!

Jim

Don M

Jim, I remember the long conversations we had about your twin turbos several times last year. You had the 16 housing and I argued the larger housing ( 18.5 or 21 CM ) and the wastegate change you now have is paramount. You had the wategate dumping into the downpipe and by-passing the 3B.

I felt you should change the wastegate to dump the hot gas into the 3B to help it spool and do the bulk of the work. The larger housing for the the 35 was needed to help the overall larger amount of exhaust gas that P pumped 12 valve was capable of making. This was before the stoopid pump!

After the second conversation you did agree the change was needed and made the plans to change it. I dont think there was much if anything wrong with the twin combination you just sold. It worked well and made good power. Spool up might not have been the worlds fastest but the HP number was healthy.

The 24 valve needs a bit more spool up help over the 12, P pump trucks. I feel that Tim could make upwards of 600 HP with the 12 CM housing and the 42 MM wastegate he has now.

Tim,

I just thought about something...do you untilize the wastegate in the 12 CM housing?

Don~

StakeMan

I agree with both Proram and Don M. You need a bigger housing on the 35 and a bigger housing on the 3B. I would try a 16cm on the 35 first, if it was mine.

Timinva

Don my 35 wastegate is locked shut, but I can make it work if needed. Thinking of a top turbo like Mervs but will test it with the 26 housing first to see if it does what I want. Sure would like to see 600hp. Curious how it will dyno with the new pm3 comp compared to the drag comp. How much boost will o rings hold? By the way did a oil analysis with 3500 miles on your injectors and it came back great. Tim