high compression and boost
This is a discussion on high compression and boost within the Forced Induction forums, part of the LSx Technical Help Section category; Originally Posted by mistermike Here's the deal with compression and boost, to clear up some blatant misinformation in earlier posts. ...
01-11-2014, 01:35 PM #61
experienced low compression booster input
okay im brand new to the site but ive been thinking of a turbo ls1 build. i had a 00 ss t65 blah blah good car 345 stock hp, any ways i got a few things to ask since u seem to know whats up so check it out, this is my idea for a lasting engine unlike soo many ppl pushin high c/r and blowin em, i dont wanna stroke the heck out of it because to me thats not going to last as long and b more money butt what about a stock bore a crank a tiddly bit bigger than stock with arp fasteners 6:1 comp, ported polished heads(need help with head idea), with a mild roller cam, beast push rods, nice roller rockers of course. i wonder this because when u race who launches at under 2grand? no one ive ever seen anyway. so my turbo idea would b a single bigger turbo and not a smaller turbo i say this because the baby turbo has less lag but more heat and its harder for it to push higher boost cuz it works harder. ok now a bigger turbo can push the same psi as a little one with way less effort and b cooled easier ok (learned this from a friend that had one of the 1st 900 hp evo8 in tx if not the 1st, he explained to me the same as i did to u) well okay common sense it seems like to me and he swears by running the exact same boost as the smaller turbo the bigger one was better. ok now this goes into play with using a bigger turbo than a lil t20 somethin or w/e some one els previously posted. ok so this could run off premium 93 oct because the molecular strand is shorter(---) like that, meaning better combustion normal unleaded has a longer strand of molecules(------------) like that. i would intercool it i wouldnt have a problem making a custom fit for intercooler and id want it to y off the headers, i think a 4-5 inch stainless pipe to run the turbo then branch bak out to 3 1/2 or 3/34 stainless out the back could handle the flow until it branched back into duels and wouldnt have to travel 300 feet before it hit the engine like rear mounts. im having trouble explaining this kinda but the gist of it is to have a fast wrap nice balanced higher boost engine. i think just the stock stroke is long in a 350 anyway so that should be plenty enough to have it spooled by 2 2.5 grand at launch and i always got best track times in my nat asperated ss shifting at 5.2 ish rather than wrapping it out to more than 6 so i just kinda need some input. the moral of this is i wanna break a turbo before i destroy a block. i mean if a supra can run a t50plus no prob then so could a extra 2 more pistons lol,, riight? so im hoping for big boost ill prob run close to stock gears not tryin to drag everyday im just a firm believer in 1 snail instead of 2.. make any sense? input plz
01-11-2014, 09:30 PM #62
01-12-2014, 06:40 AM #63
This thread is 6 years old and the person you are quoting to ask a question of hasn't logged in since 2010
01-12-2014, 09:24 AM #64
I just signed up to the site yesterday i was just enjoyin bsin. dont kill my buzz i dont care how old it is lol
01-12-2014, 07:11 PM #65
OK - by all means continue to BS with yourself then
01-12-2014, 08:29 PM #66
Merry christmas! Nice car
01-13-2014, 08:23 AM #67
- Join Date
- Mar 2006
- Fort Benning, GA
- '91 turbo fox, '97 vette
Alright, to quickly address the quoted portion above, think of sizing the turbo as a balancing act. You're trying to balance response with efficiency. Generally, the smaller the turbo, the more quickly, in terms of engine RPM, it spools. The larger the turbo, the more efficient they are at moving higher volumes of air.
In my opinion, the choice between single or twin turbos comes down to a choice between packaging, complexity, and cost. It's conceptually true that being able to mount twins closer to the exhaust ports provides some advantage to twins, but in practice a well sized single can spool and make power very similar to well sized twins. More practically, a single often creates less clutter in the engine bay, and it costs less.
Unfortunately, it's not as simple as, "if a supra can run a t50plus no prob then so could a extra 2 more pistons." I believe there would be a LOT of problems trying to run a similarly sized turbo on such a large engine. First, airflow would likely be extremely limited by the exhaust-side turbine. This would create enormous back pressure in the exhaust that would create an extreme limitation on the power output of the engine. Depending on the power output you're looking for, for a 350, you'll probably end up in the 76-90mm range with a single turbo. I'd guess you'll find yourself in the 60-70 with twins.
Compound charging (super with turbo) has been tried, and in the examples I've seen, it's always worked out less efficient than using a single method.
Good luck!'97 Corvette: bone-stock 13.2@108
'91 Mustang LX: GT42-76 powered 331.
'90 GMC Suburban: Big daddy 'burban!
01-13-2014, 05:21 PM #68
One of reasons I went with a supercharger (Procharger) over a turbo - less complicated and easier to install.
01-14-2014, 07:28 AM #69
Prochargers have really come into their own recently. Just look at the heads up classes, especially the small tire classes, they have cought up and are starting to put a hurt on the turbo cars now. I especially like their new electronically controlled unit that adjusts the boost, and can be switched on the fly.
I'm looking at this unit for a 502 build I've had in the back of my mind.
I've always prefered the Prochargers for the very reasons mentioned above. Easier and cheaper to package.
03-09-2014, 12:00 PM #70
- Join Date
- Dec 2008
- Southern California
- 1998 S-10 Truck
Just to interject something into a dead thread, I went to the Garrett web site; 6.0 ltr., 1000 h.p., single turbo, a/f ratio at 11.5 tp 1, BSFC at .46 and a 2v at .080 VE, a/a intercooler, and 1lb pressure drop = .070 effectiveness, my area "BARO" = 14.71 at 68' F., 21 lbs boost at 4k = 658h.p. at 58.06 corrected airflow, (lbs/min), and the same boost at 6000 is 1001 h.p. at 88.26 lbs/min. They recommended the GT4708 turbo.
I would be using a 10-1 comp engine and LS3 heads, with a cam with 114' lobe centers, but would need 110 octane at that boost, even with an intercooler. I could get by with 9.2-1 and not have to use race gas, pump gas at 93 and less boost, 15lbs, but still get 550 at 4k and 875 at 6k with a smaller turbo.
Just my 2 cents.....
11-16-2014, 07:47 AM #71
- Join Date
- Nov 2014
what makes you think, you need 110 octane? is that ron? doing e85 would be the solution.
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