How Much low Boost with STS set up and 8.5 to 1 Comp?
How Much low Boost with STS set up and 8.5 to 1 Comp? I built a Turbo motor for my STS system. Custom cam, forged internals, and 8.5 to 1 comp. I planed to Run low boost at about 8 or so PSI (Lg Yellow spring). However I did not think about the intake air temp. SO now I got a few questions for you. Will the 8.5 to 1 ratio help to offset the Air Intake Temp and or would you think going down a few lbs on the low boost settings might be advantagous? I can always go up a few on the HIGH setting to hit my ultimate target! Low is just gona be for driving around and what not. If I want to race someone its going to be switched to high! What do you think. I plan to Spray Meth on HIGH boost. I Guess I am wondering whats the Highest boost you guys think I should run on Low boost? Thanks for the help, Lata, Ark
TECH Fanatic
Joined: Sep 2003
Posts: 1,937
Likes: 0
From: "Tr"Asheville
The highest boost you can run will depend on how your engine is built, your turbo sizing etc. Are you using a 5.7 or an iron 6.0L block? If you are using the aluminum block then with head studs and o-ringing your not going to get much past 17-20 tops from what I have seen. The reason being is that the aluminum flexes so much that you will lift a head at those boost levels. As for the iron blocks I have heard of people running 22-25psi without any problems. This is assuming you have the correct components to hold it together, ie. o-ringed block (stainless steel o-rings) with receiver grooves cut into the heads and a copper head gasket. As for the low boost and around town driving, let's put it this way; when I had my forged 6.0L and custom rear turbo setup (T70) running 5lb's of boost it would break the tires loose from a 70 roll, and that's going through an A4. So, for street use a lot of boost will be a waste, you won't go anywhere. Hope this helps.
-Sly
-Sly
Thank you very Much for the reply! That was not what I was looking for exactly so let me try to be a bit more specific. First of I Have a LT1 Iron Block. The motor is built to take the BOOST. Don't plan on going much past 16 to 18 on High Boost.
My concern is around The Air Intake Temps on low boost. AS I said I have the Lg Yellow spring which I think = 8 or 9 lbs on Low boost. I was told that Much low boost Might hurt me (as far as tuning and Timing) when I went to high boost and sprayed the meth. I was wondering if it might be a better Idea to drop the Low Boost (change the spring) to about 7 or so lbs on LOW boost. Hopefully that would allow for more aggressive timing on low and NOT Hurt me as much when I went to High and sprayed the meth. The thing Is I don't know if its necessary? I can get to 17lbs on high no matter if I start at 7 or 9 Lbs on the low side! I was wondering what you guys thought? I just don't know so I was looking for some of you guys with experience to help me out with some advice. Thanks in advance. Lata, Ark
My concern is around The Air Intake Temps on low boost. AS I said I have the Lg Yellow spring which I think = 8 or 9 lbs on Low boost. I was told that Much low boost Might hurt me (as far as tuning and Timing) when I went to high boost and sprayed the meth. I was wondering if it might be a better Idea to drop the Low Boost (change the spring) to about 7 or so lbs on LOW boost. Hopefully that would allow for more aggressive timing on low and NOT Hurt me as much when I went to High and sprayed the meth. The thing Is I don't know if its necessary? I can get to 17lbs on high no matter if I start at 7 or 9 Lbs on the low side! I was wondering what you guys thought? I just don't know so I was looking for some of you guys with experience to help me out with some advice. Thanks in advance. Lata, Ark
Not exactly sure what you are asking, but even at 8psi, with the STS you need something to cool the charge air. If you will not have an intercooler, then you need to set up the meth so it will start to spray at 6 or 7 psi and above. You tune for the highest boost you will run. You can always set it up to run 5 or 6 w/o meth and when you turn it to high boost, arm the meth to start spraying at the same time. Hope that helps a little.
TECH Addict
Joined: Nov 2001
Posts: 2,659
Likes: 1
From: Bellevue, Wa
why don't you just make your life easier and add an intercooler?
I don't know the LT1 but the LS1 you have a real hard time going past 5psi non intercooled without pulling pretty much all your timing, but then again thats stock compression.
my brother runs 9psi non intercooled with 21 degrees advance on his 9:1 mustang all day long.
I don't know the LT1 but the LS1 you have a real hard time going past 5psi non intercooled without pulling pretty much all your timing, but then again thats stock compression.
my brother runs 9psi non intercooled with 21 degrees advance on his 9:1 mustang all day long.
8psi uncooled is doable at 8.5:1, but to run more you must use an IC anyway. I'd just get the FMIC in there and work with it from the get go.
For daily driving, I tune for low boost mode, and then set my high boost (with meth) for the highest amount I can get without knock. This way I have an optimal tune for the mode that the truck is in most of the time. If you're always cruising around at max boost, this method would be bad
Boost is limited by the denotantion threshold you're facing. DT is affected by boost, timing, fuel tuning, octane, compression ratio, and temperature (both IAT and ambient). With a lower CR, the others have more give, but somethine has to accomodate higher boost.
For daily driving, I tune for low boost mode, and then set my high boost (with meth) for the highest amount I can get without knock. This way I have an optimal tune for the mode that the truck is in most of the time. If you're always cruising around at max boost, this method would be bad
Boost is limited by the denotantion threshold you're facing. DT is affected by boost, timing, fuel tuning, octane, compression ratio, and temperature (both IAT and ambient). With a lower CR, the others have more give, but somethine has to accomodate higher boost.
The lower compression will help a little with the higher IAT, but not a whole lot. From what I understand the IAT will suddenly spike at some boost level. That would be the threshold to find and stay under when not on the meth. You might have to experiment, monitoring the IAT's. 8 is probably the limit though, maybe a little under. The lower compression will mainly help with higher boost pressures, more than it helps with IAT's.
Trending Topics
GUYS - thank you very MUCH. This is exactly what I was looking for. I may and Probably will go with a FMIC. The More I read the More I realize that its probably gona be a MUST have thing. I will spray the meth as soon as It goes past my low boost setting, I think I am gona drop that low boost setting to 7 or so. It does seem like this is gona take a while to get it right BUT thanks to helpful guys like you I am sure I will get it right! I am guessing that dropping one spring size will get me close to that 7psi range (that would be the stiffest Small spring - Blue I think). Any other input is welcome. Thanks again for the replies. lata, Ark
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo I see! Well I have the Small red and I have the Lg Yellow spring's NOW. I forget the Bar designation BUT one is too low and One is Too high. There are 2 springs that were inbetween the 2 that I have now. I ordered both of thoes springs today. SO I think I will have 4 consecutive sized springs and I hope to be able to find a sweet spot with one of them. I got the Bar/color refrence from the TiAL site BUT I just cant remember what they were now. Thank you very Much for the Help. I am sure I will have More question in the future BUT once I get this thing Up and running 1/2 way decent I will post my results! Lata, Ark
I Just went and Looked. This is the chart I was refering to.
WG38/40mm
BAR PSI
.25 3.63 Small Yellow
0.4 5.80 Small Red
0.5 7.25 Small Green
0.6 8.70 Small Blue
0.7 10.15 Big Yellow
0.8 11.60 Big Red
0.9 13.05 Big Green
1.0 14.50 Big Blue
I Just went and Looked. This is the chart I was refering to.
WG38/40mm
BAR PSI
.25 3.63 Small Yellow
0.4 5.80 Small Red
0.5 7.25 Small Green
0.6 8.70 Small Blue
0.7 10.15 Big Yellow
0.8 11.60 Big Red
0.9 13.05 Big Green
1.0 14.50 Big Blue
