Okay, I have to admit, I'm not up to speed on turbos yet but I'm selling my new D1SC tuner kit for LS1M turbo kit. My questions is what turbo should I get? I'm building a forged 6.0 (375ci) with stage II 6.0 heads. I found a good deal on a new T-76 p-trim turbo for $900. I really wanted a q-trim (bigger exhaust wheel). Can the p-trim be converted to q-trim and how much would that cost? Is a T-76 big enough for 375ci? Will it take forever to spool with this turbo? One shop suggested a T-74. The car will driven at high altitude (Denver) if that makes any difference. I'm open to all turbo suggestions here. Thanks in advance.

 

i dont know a whole lot of the trim for turbos
i couldnt tell you the difference

for the exhaust wheels might whelp you with spool, but with 346ci youll be pushing it well.

 

Q trim is a more efficient wheel, but for where you are at, I'd stick with the P trim. When/if the turbo needs a rebuild, have a better wheel put in, maybe the newer Garrett GT series stuff. To do the upgrade, you are talking parts & labor, might be a couple hundred bucks (parts = new wheel & shaft, labor = disassembly, reassembly, balancing).

FWIW, the Q trim wheel is a bastard wheel - it is created by taking a P trim wheel, welding material to it, then shaping/grinding it down.

It works, but down the road, you'll be better off with one of the newer wheels that Garrett makes.

 

Hey Brian. I seen your name many times when I had my 2 Typhoons. Thanks for the info about the g-trim. I just talked to a local turbo shop here (Turbo Engineering) and they said the same thing. The wern't fond of the g-trim.

Awesome projects you have BTW! <img border="0" alt="[worship]" title="" src="graemlins/gr_hail.gif" />

Still miss the Typhoons. To make up for it, I'm attemping to install Sy/Ty exhaust manifods on my 98 Blazer ZR2 4.3 and do custom crossover/d-pipe with custom programming. I hope it works.

 

Aside from those who apparently cannot spell, the turbos you suggest are more than enough to support the smallish engine you're building. You may consider a T-70 series. At 385, it's not that big. Go as small as possible to accomplish the job. I'd say T-72 at most. It will run well.

SC-

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by SS00Blue:
<strong> Aside from those who apparently cannot spell, the turbos you suggest are more than enough to support the smallish engine you're building. You may consider a T-70 series. At 385, it's not that big. Go as small as possible to accomplish the job. I'd say T-72 at most. It will run well.

SC- </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Spelling??? <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> "attemping" should be "attempting" and "manifods" should be "manifolds". What else did I spell wrong? <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" />

Thanks for the advice on the smaller turbo's. Maybe I should look at those. I found a chart last night that sugessted a T-76 for 350-400ci so I was just going off that chart. I realize bigger is not always better. I'll also be talking more with LS1M and see what they suggest.

 

Rodent,

I know of a guy that makes a turbo kit for the 4.3 liter S-series trucks, call Bill Mach @ Mach Performance in Clinton Twp. Michigan, 586-468-6300. Tell him Jason sent you, and he'll take care of you.

 

im sticking with the 63mm that comes with the kit because even it is rated for more than my goal, which is 600rw pump gas.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by smokinHawk:
<strong> A T-76 will support around 900fwhp, is that enough?
My T-76 has full boost (10psi) at 3k, is that soon enough? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">that 900hp rating is with the q-trim wheel. With the p-trim wheel, trim that number down about 15-20%

 

A T-76 will support around 900fwhp, is that enough?
My T-76 has full boost (10psi) at 3k, is that soon enough?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by smokinHawk:
<strong> A T-76 will support around 900fwhp, is that enough?
My T-76 has full boost (10psi) at 3k, is that soon enough? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif"><img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> <img border="0" alt="[gruffy cottonball]" title="" src="graemlins/gr_gruffy.gif" /> <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />

Whats your opinion on the q-trim?

 

I've made ~600+ hp on a p trim 63, and a friend has made 700+ hp on a p trim 72. I wouldn't say the p trim cuts it down that much.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by rodent:
<strong>Spelling??? <img border="0" title="" alt="[Roll Eyes]" src="images/icons/rolleyes.gif" /> "attemping" should be "attempting" and "manifods" should be "manifolds". What else did I spell wrong?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Sorry, rodent. I was poking fun at someone else. In either case it was just for fun. Sorry for the humorless humor.

The best road is always what works for your application without overkill. A turbo too large will negatively impact drivability and make it difficult to get the PT tuning spot on, and that's really the biggest plus for a turbo. PT is like bone stock, but it's an animal at WOT. You might just talk directly to Precision Turbos and Engineering. They've got the stink on turbos...

I love turbos.

SC-

<small>[ January 29, 2003, 07:06 AM: Message edited by: SS00Blue ]</small>

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by JimmyKash:
<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 smokinHawk:
<strong> A T-76 will support around 900fwhp, is that enough?
My T-76 has full boost (10psi) at 3k, is that soon enough? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">that 900hp rating is with the q-trim wheel. With the p-trim wheel, trim that number down about 15-20% </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Besides what I mentioned about the p trim numbers, I think that people need to remember that the quotes that you see from PTE & Turbonetics etc, are high end numbers, from what you'd see from pushing big boost (30+psi). Most of the 70 series turbos see their best efficiency at 20-28psi, but not supporting the max quoted hp at that point, typically you have to run even higher boost, slightly out of its efficiency map, to get that much. So to get 700-1000hp from lower boost levels (this is 10-20psi in my book), you'd need 88-100 series turbos IMO.

 

Brian - I was wondering if anyone was going to bring up the efficiency thing. I've been looking at different compressor maps for a while now and it seems that for a 370ci motor with appropriate heads/cam/exhaust a 88 is the only single that will be operating within an efficient range @ 10+psi. The T76 was off the map it was so far outta it's most efficient range on the motor I described above.

So I have a question for the turbo guys here. Is the turbo efficiency that big a deal with a properly setup intercooling system(whatever is used) or are the turbos absolute airflow capabilies more important?

Kinda off the topic....well maybe not. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

One other thing. A T76 can spool up on these motors by 3000rpm, Is a T88 going to take that much longer to spool?(I've heard 4000rpm before) It might actually be beneficial if you were running 700+hp for the boost to come in a little more gradually rather than INSTANTLY. <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

John

 

Almost any turbo system is going to be a compromise, if you map out the airflow needs, you'll see where it lies on the maps of different turbos and what you'd give up.

If you are WAY off the map, then yes, it's a big deal IMO, and you might as well go back to supercharging <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> You'll probably be pushing safety issues. Some form of intercooling is really necessary on turbo systems IMO, so by saying you have a good intercooler, it isn't going to help matters much.

I've seen bad turbo combinations, and they suck. Undersized = boost out of control, high charge air temps leading to detonation, could even destroy turbos by overspeeding them. Oversized = crappy performance due to lack of response, airflow may not be at peak efficiency, and just doesn't provide the performance that it could.

As far as spool - yes it will suffer, but exhaust housing selection, converter, the calibration and motor buildup will change its characteristics.

I tuned a Supra powered Lexus with an 88 turbo (and a turbo 400 tranny <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> ). Yes spool sucked, BUT it was a good selection for a turbo, as response was linear... if boost came up quickly, it would have had HUGE wheelspin problems. When it was done, it had 850rwhp that was streetable; the turbo helped act as a form of traction control. Matching the turbine housing will help a bunch. In fact, some road racing cars would go to an enormous exhaust housing to avoid boost rising too quickly and blowing out the tires while accelerating out of corners.

Most of the bigger turbos love higher pressure ratios (15-30psi), and don't do well at lower pressure ratios. It sort of sucks to have to run low boost on the LS1 kits, but again, it's a compromise. If you can build a motor with 8.5:1 CR and run 15-20psi, you'll make awesome power, compared to running 10:1 CR with 5-10psi. Unfortunately, the LS1 heads don't like to stay on too well with higher boost.

 

oh come on bgreen, you know 'boost' has nothing to do with cylinder pressure.. thats just hp

15psi boost making 600rwhp has the same cyl pressure 5psi 600rwhp

boost is just a measurement of intake backpressure between the valve and the turbine wheel.


thats why i wont mind running 15psi on the 63 to make 600rw.. the cylinder pressures are the same as a 76 at 10psi exept, im in the eficciency range so i get optimum spool, and that awesome low end tq that goes along with it..

of course i am assuming the ls1m intercooler can handle the slighly higher inlet temps.. but im not worried.. that fugger is huuuge! <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

<small>[ January 29, 2003, 01:32 PM: Message edited by: MIGHTYMOUSE ]</small>

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by SS00Blue:
<strong> Sorry, rodent. I was poking fun at someone else. In either case it was just for fun. Sorry for the humorless humor.

The best road is always what works for your application without overkill. A turbo too large will negatively impact drivability and make it difficult to get the PT tuning spot on, and that's really the biggest plus for a turbo. PT is like bone stock, but it's an animal at WOT. You might just talk directly to Precision Turbos and Engineering. They've got the stink on turbos...

I love turbos.

SC- </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No problem. I thought that was directed at me. I do tend think faster than I can type.

I'm totally with you on getting the right turbo without going overboard.

Lot of good comments here! Thanks! <img src="http://coloradof-body.com/ubb/graemlins/ShiftinSmiley.gif" alt=" - " />

 

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

Most of the bigger turbos love higher pressure ratios (15-30psi), and don't do well at lower pressure ratios. It sort of sucks to have to run low boost on the LS1 kits, but again, it's a compromise. If you can build a motor with 8.5:1 CR and run 15-20psi, you'll make awesome power, compared to running 10:1 CR with 5-10psi. Unfortunately, the LS1 heads don't like to stay on too well with higher boost. </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I still think you can get great power with 10:1 @ 10 psi. For example look at the LS1M kit. Thats incredible figures on a stock motor! Another example is someone here locally. 2001 Z06 running a 427 with 10.3:1 CR and an ATI D1SC @ 8lbs. He dyno'd 697rwhp and 710rwtq and is currently the top of the dyno charts here in Denver (www.dynopro.com). I agree about the heads lifting. I hope o-ringing the block will help.

<small>[ January 29, 2003, 11:23 AM: Message edited by: rodent ]</small>

 

</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:
<strong> oh come on bgreen, you know 'boost' has nothing to do with cylinder pressure.. thats just hp

15psi boost making 600rwhp has the same cyl pressure 5psi 600rwhp

boost is just a measurement of intake backpressure between the valve and the turbine wheel.


thats why i wont mind running 15psi on the 63 to make 600rw.. the cylinder pressures are the same as a 76 at 10psi exept, im in the eficciency range so i get optimum spool, and that awesome low end tq that goes along with it..

</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Sorry but no, running more boost with lower compression WILL make more power than less boost with higher compression; when you keep the effective compression ratio the same. This has been proven many times over, and the same discussion has been had in the TurboBuick world. You *rarely* see anyone running higher compression over there, instead you see sky high boost levels. Some run *slightly* elevated compression, to help spool up & response at the line, but those are all out race cars, running large turbos, who will sacrifice some power for better reaction time & boost response. Typically their 'elevated' compression ratio won't go higher than 9.5:1.

15psi on a 63 (2:1 ratio), flowing air for 600hp has you falling out of peak efficiency, probably near 60% efficiency. 15psi on a 76 (2:1 ratio), flowing the same amount of air, puts you right in the peak efficiency, 76-78%. I was running ~21psi on a 63 (2.3-2.4 pressure ratio), making in the neighborhood of 600-625hp. That is just starting to fall right out of the efficiency island. On my fastest runs, I saw my boost level dropping down a bit at the end of the run, and my intake temps dropping. An upgrade was in order at that point.

As far as making power with higher compression and low boost, sure, it can be done... but if you did it the way I am saying, low compression and slightly higher boost levels, you'd make excellent power as well, and probably done safer.
Harlan's is a good example. If he had a motor that had a bit more clamping power on the block & bulletproof innards, I'm sure he'd run even higher boost levels.