Tuning Twins

So what if I swapped in a 66/73/.70?


It should relieve more drive pressure overall, but still have quick spool up with the tight housing...or am I barking up the wrong tree?

I like the quick spoolup of the .70 housing and 68mm exhaust wheel I have now, but I don't like the overall high drive pressure to boost ratio.

I was able to finally get almost 30 psi out of the primary, but the bottom end was so slow, Smokey, and hot, I didn't push it for too long.
 
Jim Fulmer said:
The math that is posted is odd to me in many ways, I've run (not currently) over the years a few twin setups and my data is a bit different. The setup in my avatar is an HX-40-16/ HT3B-26 with a divorced gate setup using the internal gate (like the old Piers twin setup) it was running at 60 psi total with the 3B making 33-35 psi and drive pressure at 65......just info for you!

Jim
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For the record I am seeing the same results with the same set up. Just put down 669hp with it a DIY CP3 and 90hp DDP inj. a cam and studs. This is in an ealry 04.
 
Can anyone offere some advice. As of right now I'm running a Hx40 in my compound set-up, but it might be sold. Would a 62mm turbo with a 12 or 14 be better? The Hx40 is just a tad laggy.

I figured that a smaller turbine but heavier wheel would equate the same spool time, but cooler temps. But maybe the 12cm housing would be best for a street set-up daily driver, but I don't want to drop off in the higher rpm's.
 
What is everyone using for a Drive pressure gauge filter? Getting ready to start putting my compounds on and want to have everything when I start.
Thanks
 
kydecoy said:
What is everyone using for a Drive pressure gauge filter? Getting ready to start putting my compounds on and want to have everything when I start.
Thanks
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Steel wool

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Headcase98002 said:
Can anyone offere some advice. As of right now I'm running a Hx40 in my compound set-up, but it might be sold. Would a 62mm turbo with a 12 or 14 be better? The Hx40 is just a tad laggy.

I figured that a smaller turbine but heavier wheel would equate the same spool time, but cooler temps. But maybe the 12cm housing would be best for a street set-up daily driver, but I don't want to drop off in the higher rpm's.
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Going off of the advice of ronA(1200+hp), he said a hx40 was very similar to a 62.

So you probably just need more tuning. JMO
 
bsmith said:
Going off of the advice of ronA(1200+hp), he said a hx40 was very similar to a 62.

So you probably just need more tuning. JMO
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Seriously? Wow, i hope I see some benefit of the 62/65/12 I'm buying today. It will definately spool better that's for sure. I've always been told the Hx40 compares to the s300g.
 
I'm getting more in depth with my turbo tuning and I'm having some issues with compressor maps. How do you figure cfm in a compound system? Is it as simple as using the PR and multiplying it to the n/a cfm number? In my figuring a 5.9 at 3500rpm could use around 360 cfm and my primary is running real close to a 3.0 PR. So would that be 1080 cfm?

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I might have found my answer. The calculation I found is (displacement in liters x rpm x ve x PR) / 5660, so for mine I went with (5.9x3500x90x3)/5660 = 985 cfm / 14.27 = 69 lb/min. Does this sound correct? It puts me in the .76 efficiency island.

I don't think I used ve in my original calculation. 1080x.90 = 972 which is pretty close to my second answer.

Any feedback would be great. Thanks

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Your VE is not going to be that high. More like 60-65%

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jkidd_39 said:
Your VE is not going to be that high. More like 60-65%

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That low? I'll redo my figures then, it'll look a lot better on the map.

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Good thread here :)

I'll be setting up my twins this weekend or next, had my secondary adjusted too low (20lbs) and it would bring on the primary, but there was no real surge in power. Need to pick up a second boost gauge to see what the primary is up to.

EGTs are low, at the 38lbs total boost I was only at 1100. Heavy on the smoke, need to pull the star wheel back and turn the preboost screw out a a 1/4. Rolling into it I get a decent grey haze, want to bring that down as much as possible.
 
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I'm thinking about going to a 62mm compressor on top and it seems that alot of guys don't like the 65mm turbine wherl. Should I ditch the 65 turbine and just go to a 68 or could I make up the shortcomings of the hot side with an external gate? The setup I have is working pretty good with the VP but I'm going to p-pump it in the near future and I'm preparing for the extra fuel.

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chevota84 said:
I'm thinking about going to a 62mm compressor on top and it seems that alot of guys don't like the 65mm turbine wherl. Should I ditch the 65 turbine and just go to a 68 or could I make up the shortcomings of the hot side with an external gate? The setup I have is working pretty good with the VP but I'm going to p-pump it in the near future and I'm preparing for the extra fuel.

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Id stick with the 65 turbine unless your not concerned about spool up.
 
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