side by side twin turbos?

JAyers93 said:
Yes 45-50psi with 70 total every time i put the pedal to the floor. I know thats not exactly a tuned set but do you suggest I do about it?

Sorry Willy91 for the hijack!
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50psi is a bit much from a 3B...35-40psi would be better, but I've heard your truck runs pretty well. Looks like the 3B needs a gate of it's own though, if you are that worried about it.


Willy91...I'll grab some measurements sometime, I promise:D:D If you wanna come get it next week you can though!

Chris
 
its not a 3b its a 4B with a 26cm exhaust housing. Deppending on where I have the s3's gate set at i can get anywhere from 43psi to 50psi from the 4B. I tried a 3b with a 32 and a 26 to see if it would help my spool up but the 4B feels much stronger and spools just as fast or faster then the 3B with the 32cm. I think water to air and some afc tuning will help with the spoolup issue.

Do you still think I would gain from a external gate now that you know i have a 4B?
 
Don't know jack about a 4B...how big are the wheels??

50psi is probably still high at 70psi overall, but if it works, why worry about it? Unless you can make it better at least!

Chris
 
JAyers93 said:
its not a 3b its a 4B with a 26cm exhaust housing. Deppending on where I have the s3's gate set at i can get anywhere from 43psi to 50psi from the 4B. I tried a 3b with a 32 and a 26 to see if it would help my spool up but the 4B feels much stronger and spools just as fast or faster then the 3B with the 32cm. I think water to air and some afc tuning will help with the spoolup issue.

Do you still think I would gain from a external gate now that you know i have a 4B?
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Have you tried setting the gate to open later on the 62( like 25-30psi)? it would probably help spool up time
 
With manifold pressure of 70psi and a first stage running 50lbs, your second stage isn't doing.... well anything really.

At 70 overall and 50 first, the second stage is making a whopping 4.5psi at full song.

Now are you sure you're in fact running 50 on the first stage alone? And if so, what kind of gate do you have on the second stage? My lord. To hold the small charger down to 4.5psi while you drive the big charger to 50psi is no small task.

That's a lot of wastegating. The gate would need to be damn near as big as the second stage turbine outlet.

IIRC, my best boost/drive ratios when running ~70lbs on the manifold were had with a first stage pressure of ~25psi.
 
i think that he is saying his primary charger is making 50 and his secondary charger in making 20....totaling 70psi
 
coon smile said:
i think that he is saying his primary charger is making 50 and his secondary charger in making 20....totaling 70psi
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Newsflash...

If the first stage was making 50, and the second stage was making 20.... the manifold pressure would be 138 PSI!.

Hence my original question of just exactly how much boost is he running on this truck if the first stage is at 50...


For instance:

When I'm running ~70lbs on the manifold, I will usually run ~25lbs on the first stage and ~17lbs on the second. Pressure ratios of ~2.7 and 2.1 respectively.
 
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coon smile said:
i think that he is saying his primary charger is making 50 and his secondary charger in making 20....totaling 70psi
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Charles beat me too it:D :D



Me personally, I like to make a primary work a little warder than 25-30psi...they were designed to run at higher boost than that on the trucks we took them off of, I say let them work a little:D

Chris
 
easy buddy, i have just never seen or heard of a calculation like that...

i was always told that you want a ratio of 1:1 b/n the two chargers when compared to the total boost (measured at the intake)

ie. if your gauge (tapped at intake) reads 60 psi total, you want the gauge reading the primary charger (mine is tapped in the cold pipe) reading 30 psi
 
Kyle...that is just simplification...there is more involved with the compounding than most know...I know enough to be dangerous on the practical side...Charles has the math figured out it seems:D


Chris
 
coon smile said:
easy buddy, i have just never seen or heard of a calculation like that...

i was always told that you want a ratio of 1:1 b/n the two chargers when compared to the total boost (measured at the intake)

ie. if your gauge (tapped at intake) reads 60 psi total, you want the gauge reading the primary charger (mine is tapped in the cold pipe) reading 30 psi
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Well, in that case the first stage would be doing almost exactly twice as much work as the second stage.

It's not a case where 30psi from one stage and 30psi from another means equal work. In reality, if you did that, the truth is that the first stage would be doing a pressure ratio of ~3.04 vs a second stage pressure ratio of only ~1.6 or so. Hence the fact that it's working around twice as hard.

That big charger would be working overtime and the little one would be doing it's impression of a ceiling fan making the equivalent of ~10lbs of boost.
 
those numbers dont really do much for me...i need some kind of equation to interpret this
 
Signature600 said:
Kyle...that is just simplification...there is more involved with the compounding than most know...I know enough to be dangerous on the practical side...Charles has the math figured out it seems:D


Chris
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im surprisingly good with math....humor me....
 
Charles said:
Newsflash...

If the first stage was making 50, and the second stage was making 20.... the manifold pressure would be 138 PSI!.

Hence my original question of just exactly how much boost is he running on this truck if the first stage is at 50...


For instance:

When I'm running ~70lbs on the manifold, I will usually run ~25lbs on the first stage and ~17lbs on the second. Pressure ratios of ~2.7 and 2.1 respectively.
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haha i know what 136 psi looks like (not my truck)
 
coon smile said:
those numbers dont really do much for me...i need some kind of equation to interpret this
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Thats the bueaty of compounding correctly, the motor sees 70,80,90 psi and the chargers are down there working nicely within there map.
 
coon smile said:
those numbers dont really do much for me...i need some kind of equation to interpret this
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Look at a compressor map, the verticle axis measures in pressure ratio's, not PSI. Discharge pressure vs. intake pressue. If the intake pressure is atmospheric, 14.7 psia, then a 2:1 PR would be 29.4 psia (PSI Absolute). Since just about no one runs a PSIA gauge, it will be PSIG (PSI Gauge), which is less atmospheric pressure. So at a 2:1 PR, you would be seeing 14.7 psi over atmosphere. If you were running a 4:1 PR, it would be 58.8 PSIA, 44.1 PSIG over atmosphere.

If your primary is working at a 3:1 PR, discharge pressure would be 44.1 PSIA, 29.4 PSIG. If your secondary is working at a 2:1 PR, discharge pressure would be 88.2 PSIA, 73.5 PSIG. If your secondary was working as a single at that PR, it would only produce 14.7 PSI boost. By being fed higher intake pressure, it is now producing 44.1 PSI over what it took in, while maintaining the same PR.

If the primary is producing 50 PSI of boost, its at 64.7 PSIA, which at sea level would be 4.4:1 PR. If total boost is 70 PSIG, 84.7 PSIA, and interstage pressure is 64.7 PSIA, the PR is more like 1.3:1. At that PR in a single turbo configuration would only produce 4.5 PSI boost.
 
You guys are confusing the hell outa me. I have a boost guage that is hooked into the intake manifold on the head. I see 70psi at that point. And I also have a guage that takes a reading in between my chargers and it sees 45-50psi.

The HT4B is an 82 or 84mm (ICRE) inducer with a high 80's or very low 90's mm turbine exducer. An i have a 26cm exhaust housing. Surly 50psi is not pushing a charger this size outa it map. Hell people ive only got a damn VE IP!

And Charles I see where your coming from but ive never heard of it being does this way. Then again I haven't been throughly educated in the subject either.

Im still running the internal wastegate in the S300.

I always thought....correct me if im wrong....but the little charger (secondary) gets the big one (Primary or atmosphere) going then lets the big one do most of or at least close to the same amount?
 
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JAyers93 said:
You guys are confusing the hell outa me. I have a boost guage that is hooked into the intake manifold on the head. I see 70psi at that point. And I also have a guage that takes a reading in between my chargers and it sees 45-50psi.

The HT4B is an 82 or 84mm (ICRE) inducer with a high 80's or very low 90's mm turbine exducer. An i have a 26cm exhaust housing. Surly 50psi is not pushing a charger this size outa it map. Hell people ive only got a damn VE IP!

And Charles I see where your coming from but ive never heard of it being does this way. Then again I haven't been throughly educated in the subject either.

Im still running the internal wastegate in the S300.

I always thought....correct me if im wrong....but the little charger (secondary) gets the big one (Primary or atmosphere) going then lets the big one do most of or at least close to the same amount?
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Not quite. They are called Compound turbos for a reason.

But lets back track a minute and talk about turbos in general. They don't care about pressure. They could be putting out 30 psi or 90 psi it doesn't matter. WHat they DO care about is Pressure RATIO. The ratio of the air leaving the turbo in relation to the air entering the turbo. Look back up at Tate's post he explained it pretty well.

Now back to the compund turbos.The primary compresses the air(that would be the FIRST stage of compression) and then sends it to the Secondary. The secondary then Compresses the air again(The second stage). It's not just sitting there freewheeling. It's working its butt off if the twins are setup right. They are set up this way so that you can acheive higher overall boost pressure while keeping both turbos well within their efficient range.
 
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