Sears

Just pondering, tell me if my thinking is flawed..

On a V configured engine ( or flat ), I would think Twins would be superior over a single. Powering one turbo off of both manifolds would increase ( 2x ) the flow rate to the ( 1 ) turbine therefor increasing the operating temperature of the turbo right.

Would you see considerable power/heat loss from the cross tube on the single kit?

With a true twin turbo using a turbo off of each manifold, operating temp of the turbo would be much lower. But then again the larger single turbo is more efficient, creates less backpressure, then a smaller turbo ( x2 ).

How great are the heat differences between the single and the twins? Reducing the mass flow rate of the turbo in half would reduce the heat by what ?

Incon is dead but other twin LS1 kits are in the works. How are the incon kits synchronizing the wastegates or are they only using one? Are they using discarhge pipes from the turbo?

I know people like to compare to Supras, and say single is better but I don't see how this can be true in our application. Keep in mind a street driven car, boost in the 8-15psi range, rev limit in the 6500rpm range...

Thanks,
Justin

<small>[ December 12, 2002, 07:13 PM: Message edited by: Jsears8 ]</small>

FASST

twins would definitely be a better design for a V-configured engine.

The heat loss due to the cross-over pipe depends on allot of things: Operating temp, Ambient temp, flow, material construction, pipe location. At high rpm (max flow rate) the dissapation would be minimal. From the pictures I've seen of the LS1MS kit, it looks like the pipe goes under the bottom of the car which will expose it to a fair amount of outside air (oposed to routing through the engine bay which would be very close to operating temp). This placement will help in cooling, but assuming ~300cfm, not much. Enough about the cross-over pipe.

A twin setup will benefit from a twin intercooled setup (most designs have more surface area in a twin configuration than a single). At first glance it would appear that the heating effects would be the same (IOW, two turbos, twice the heat). But, the turbo is at a constant temp during operation, therefore there would be no more heat absorption per volume of air.

I hope this answers your questions...or at least gives you a platform to inquire further. Lets hear some other opinions of benefits/shortfalls of each system. Good post!

MIGHTYMOUSE

iTrader: (59)

a properly configured and sized single turbo will always overpower a twin turbo.

i have not much factual evidence backing this, but Matt said so <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />

i'll reply again after i think about it some more <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

MelloYellow

Ya, with current turbo spool ups not being such an issue anymore and the amount of air our LS1's push, I don't see why anyone would want the twins anymore.

Can someone help explain to me why we'd want the complexity/cost of the twins and what the advantages are? We don't seem to have much single turbo lag.

mexSSican

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>Can someone help explain to me why we'd want the complexity/cost of the twins and what the advantages are? We don't seem to have much single turbo lag.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Turbos are like *********...sure you could function perfectly with one ********, but would you want to?...if you only have one, it just isnt normal <img border="0" alt="[jester]" title="" src="graemlins/gr_jest.gif" />

Rpm2800

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MIGHTYMOUSE:
[QB]a properly configured and sized single turbo will always overpower a twin turbo.

QB]</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't know about that.

chasgiv3

iTrader: (1)

What size single turbo would you need for say 1000HP crank? Say at least 800RWHP. I've only done research on Twins so I'm a little out of my element. You have to remember that a large Turbo will require more exhaust pulses to get going than a smaller one. However a single gets the benefit of twice the amount of pulses. So....is there really any difference? I don't think there's much. However part of the exhaust that creates a good strong pulse is the heat generated by the combustion. Any piping that allows the turbo to be placed too far away from the header will allow heat loss and thus pulse impact loss. Another byproduct is increases heat within the engine compartment.

However again a twin turbo setup requires two turbos, two wastegates, two hose lines two intake lines, etc. But the twins would be a symetrical load on both sides of the motor (in theory). A single may have non symetrical load depending on piping and length.

Honestly I don't think there's much of a difference. HOWEVER....why are all these HP crazy SOB's going twin turbo or even quad turbo? I've heard different stories as to why. Just not quite sure of the truth.

Rpm2800

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Rpm2800:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by MelloYellow:
<strong>Ya, with current turbo spool ups not being such an issue anymore and the amount of air our LS1's push, I don't see why anyone would want the twins anymore.

Can someone help explain to me why we'd want the complexity/cost of the twins and what the advantages are? We don't seem to have much single turbo lag.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Spool time. Twins usually will spool faster for the same given airflow. Also more power with less boost. With something like a T76, max power(about 900hp) is at something like 25-30psi.

Most guys on here are not going for that type of power though, and like you said, spool time on the Ls1's or most V8's might not be as big of a problem as smaller motors with a bigger single.

Anyways just trying to answer the question as to the advantages off twins.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

XLR8NSS

iTrader: (4)

I was putting together combos on paper for a 422ci motor. I was trying to get the most efficient setup with both a twin and single setup for 10-12psi(intercooled) at around 850+fwhp.

It looks like one T88 can do the same thing as two 60-1 with basically the same efficiency. So what is better a 60-1 being spun off of 4 cylinders or a T88 being driven off of 8? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> Just going off of the size it seems like the 88 might have the advantage(spool time). Also, since the efficiency of both setups is the same the twins shouldn't have any advantage over the T88 in the added heat department. I don't know hardly anything about turbos though so I could be way off. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

John

<small>[ December 13, 2002, 11:23 PM: Message edited by: XLR8NSS ]</small>

Rpm2800

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by XLR8NSS:
<strong>I was putting together combos on paper for a 422ci motor. I was trying to get the most efficient setup with both a twin and single setup for 10-12psi(intercooled) at around 850+fwhp.

It looks like one T88 can do the same thing as two 60-1 with basically the same efficiency. So what is better a 60-1 being spun off of 4 cylinders or a T88 being driven off of 8? <img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> Just going off of the size it seems like the 88 might have the advantage(spool time). Also, since the efficiency of both setups is the same the twins shouldn't have any advantage over the T88 in the added heat department. I don't know hardly anything about turbos though so I could be way off. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

John</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I saw a Duttweiller(sp) small block 355 sbc make 800 fwhp with 2 T04's which I think are 60-1's or about that size. (of course there are different trims,combos. The thing about it, is this motor made power max power under 6000, and had 700lbft at 3000 rpm! Not that everybody would want that much torque that low. A T88 could make that power easy, but I don't know if it would have made that type of power that low in the Rpm range and at that boost level on a motor that size.

A T88 might be Ok on a 422ci daily driver though. Heck it might don fine on a smaller motor. I have seen a T88 on a 9second daily driven mustang. But 2 smaller ones of equal flow would probably still have an advantage. Especially on a street car.

But from what I have seen anyways, twins SEEM to have an advantage for a given boost level, and also spool time.

A T88 can SURELY make that power at probably the same efficiency as 2 smaller turbos of equal cfm, but a what PSI? And what Rpm? I think thats where the twins have the advantage.

For an equal comparsion, you also must compare a single turbo against 2 smaller turbos that flow the SAME cfm efficiently. Not just 2 SMALLER turbos.

As far as spool. I also wonder sometimes about the single being pushed by both banks vs twins having one bank each in regards to exhasut and spool up also, but it just seems to me that twins have somewhat of and advantage. It's not like singles take all day, but just that twins seem to spool a little quicker.

<small>[ December 14, 2002, 10:20 AM: Message edited by: Rpm2800 ]</small>

XLR8NSS

iTrader: (4)

I'll work out the comparison I was giving with the 60-1(TO4B's) and the T88 tomorrow or Sunday. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

It seems that on those T88 Supras the turbo is spooling up around 4-5000rpm. That's just 3liters right? A 422 is ~7liters. Would that cut the spool time in half compared to a Supra since the 422 has over twice the displacement?

This is a pretty good topic. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

I gotta go to sleep. Work tomorrow at 4:30am is gonna be here in a hurry. <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" alt="[boring]" title="" src="graemlins/gr_zzz.gif" />

John

Air21

www.turbobuick.com

they have no problem running 1200 hp with a single PT-88 on a little V6

Rpm2800

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Air21:
<strong>www.turbobuick.com

they have no problem running 1200 hp with a single PT-88 on a little V6</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">We know singles can make the power. It's been done for awhile. Most of us have seen single thumpers making 1400-2000+hp and run sixes on motors less than 400ci.

That's not the issue we are debating. It's whether or not twins have advantages, mainly in spool time, and being able to make the same or more power with less boost for a given cfm.

As far as singles making the power, that's a given.

Again, we are just discussing if there are advantages to twins, and if so what they are.

chasgiv3

iTrader: (1)

From a packaging standpont if you can nicely fit an 88 in there with a 4" downpipe then go for it.

Check out the piping on a Buick maybe you can use the same route. I've spent a lot of time under the car looking at routing. It's not easy.

I still say when you weigh all things it's not much difference going twin versus single. Matter of packaging and good control.

Not sure if there's any heat issues for the road racing guys on a Turbo that's mounted up front high. I just don't know.

JimmyKash

Just to answer a few questions and misconceptions i've read so far:

1) The supra 88 turbos you see aren't the typcial 88mm PTE turbo, they are mitsu and greddy 88 turbos which are more like a typical Garrett style 76mm turbo

2) A PTE 88 turbo can support a good 1200-1250hp. A pair of 60-1 turbos can do the same, you can even use the PT52 turbos also (which a few have shown already between Monty Williams, John Meaney, Doug Hegge, and the new car in popular hot rodding). The difference is in the spool time and street characterisitcs. Monty's vette makes 8psi INSTANTLY when he nails the throttle and he has like a 3000rpm stall and he's told me it just jumps like mad higher. I know 2 people with PTE 88s on them and they only come with one exhaust housing (.96) and you need a minimum of 4000stall. I feel twins win in the street department

3) A T80 with the new wheel out on the market (some call it R, some call it X,) can support 1000hp flywheel

XLR8NSS

iTrader: (4)

Thanks for clearing some of that stuff up Jimmy <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

I like the idea of two TO4B 60-1's sitting under the hood of my truck one day.

I just need more MONEY!!! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

John

RunNE1

iTrader: (1)

I also agree that twins are the better set-up. I imagine that the crossover tube arrangement makes for less than optimal exhaust flow. They "tune" headers for a reason. You want the exhaust pulses not to interfere with eachother. It seems that x-over tube plus the uneven lengths of exhaust tubing would lead to the above. While a larger turbo is more efficient, the size of turbos used on twin V-8s are not exactly small. Plus, the V configuration engines are more suited to twin turbos: better manifold design, better exhaust flow capability, and although not as important, better aesthetics. If you've ever read Corky Bell's book "Maximum Boost" there's a quote that should stand out, "Over 350 cid, twin turbos become a virtual necessity." I imagine this applies to our 346's. When I go turbo, I want two turbos staring me in the face when I pop open that hood. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

chasgiv3

iTrader: (1)

If you are concerned about spool time. Then make sure your turbo/turbos are closer to the heat source (exhuast ports). A twin setup will allow you to put the turbos a bit closer if you put them in the open V area. Closer to the heat source gives you a higher speed expanding driving force on the turbine section. This minimizes spool time.

I doubt a single versus twin (both properly sized for the HP goals) placed equal difference from he heat source would give you much of a difference in spool time.

Another thing to keep in mind is the type of Turbo you're buying. Depending on the wheels and whether the Turbo has bearings or not will greatly affect spool time also.

Rpm2800

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by RunNE1:
<strong>While a larger turbo is more efficient, the <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">????

More effient than what. A single smaller turbo(of course).

Or 2 smaller turbos(twins) that flow = cfm. ?????

Pro Stock John

iTrader: (34)

Let me preface my comments by saying I do not have a turbo car I am just learning right now and plan to build one in 2003.

That being said... From talking to experts in the field I see that the issues are like this...

Twins - spool up faster, lot of clutter
Singles - more lag
Singles - limited downpipe room?

I 'hear' that the Turbotech has a 2.5" downpipe which would clearly be too small for say a T76. Result could be huge tq, and low hp... (I am quoting someone else)... And i can see that too, if you pushing air thru a straw.

I've seen a GN that had a 5" downpipe that was like a low 9 second car. I wonder what size downpipe and downstream piping we would need to run to support a T76 or a T88.... 4" down pipe?