9:1 compression with boost?

S

SaturnSpeedster

Wrench Pro
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16
Location
Bartlett
Car
1997 Saturn SC2
What is the highest amount of boost that I can (safely; conservative numbers) run (from a turbocharger) on 9:1 compression, with 91 octane pump gas?
A little info on the application:
9:1 compression (as stated)
Inline 4-cylinder engine with Dual Overhead Cams, 4 valves per cylinder
cnc forged billet aluminum dished pistons with teflon coated skirts and ceramic coated tops - full floating wrist pins
cnc forged billet 304 stainless steel connecting rods with polished journals
cnc forged billet 304 stainless steel crankshaft with 8 counter weights, knife edged and polished journals
inconel intake and exhaust valves with 5-angle valve job
everything heat treated, shot peened, and balanced to 8,000 rpms

Turbocharger is a ceramic ball bearing Turbonetics t3t4b with super H compressor wheel, F1-57 turbine wheel, .48 a/r turbo housing, with Duo 35 recirculating blow off valve, Evolution 35mm wastegate, and 490hp rated intercooler. Turbo is mounted on a custom ceramic coated 4-1 header and has custom cold air piping with dual 3-inch cone filters running to the intake.
Thanks!
 
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A good post at least you have put the spec down so it warrants a sensible reply . You missed out what engine as this will help to give a more detailed answer .

First try to speak to the tuner who is sorting this or someone who has experience of running a turbo on your engine .
Failing this every turbo will have a compressor map which will show you the optimum boost range and you can work things "backwards" from there . You can get the map fromn the interwebby without difficulty.

The level of safe boost will also depend on the ECU and the map - some ecus can be mapped much more accurately thean others.
Also some engines produce more heat and are more prone to damge on high boost.


With that spec you probably have done it anyway but you have left out the head gasket on your list which should be uprated
 
The fuel choice will also have a bearing on this as well. Higher octane fuels allow you to safely run higher compression ratios.

I think 9:1 is a little on the high side and would personally look at lowering this or adding water injection.
 
SLEEPER said:
A good post at least you have put the spec down so it warrants a sensible reply . You missed out what engine as this will help to give a more detailed answer .

First try to speak to the tuner who is sorting this or someone who has experience of running a turbo on your engine .
Failing this every turbo will have a compressor map which will show you the optimum boost range and you can work things "backwards" from there . You can get the map fromn the interwebby without difficulty.

The level of safe boost will also depend on the ECU and the map - some ecus can be mapped much more accurately thean others.
Also some engines produce more heat and are more prone to damge on high boost.


With that spec you probably have done it anyway but you have left out the head gasket on your list which should be uprated
Click to expand...
The engine is a cast aluminum GM "LLO" engine, it is a 1.9L inline 4 cylinder engine with a bore of 3.23 inches (82mm) and a stroke of 3.54 inches (90mm).
For heat, I will be going 2 heat ranges colder for the spark plugs, and retarding ignition timing based on boost pressures.
Also, yes, I forgot to mention, but I did upgrade the head gasket as well.

waynne said:
The fuel choice will also have a bearing on this as well. Higher octane fuels allow you to safely run higher compression ratios.

I think 9:1 is a little on the high side and would personally look at lowering this or adding water injection.
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WOW, I completely forgot to add this, and it was the whole purpose of the post!
First off, I fully appologize for this. Secondly, allow me to rephraze my question.
What I meant to ask was, what is the highest boost pressure (psi) that I can run on a the engine with 9:1 compression AND 91 OCTANE PUMP GAS!
Thank you for letting me know I skipped that.
 
Combustion chamber design plays a part equally important as both geometric compression ratio and fuel octane rating.

May style combustion chambers were used in the Jaguar XJS HE, 5.3 litre V12. It had a 13.1:1 compression ratio.

It was not pressure charged but 13.1:1 was high when most cars were below 10:1 at that point.

The daftest bit I thought was that HE stood for High Efficency!

Someone was having a laugh. 5.3 litre V12 :) - high efficiency.

TWR (Tom Walkinshaw Racing) did successfully supercharge this engine (mechanically). Possibly the compression ratio was reduced for this application.
 
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SLEEPER said:
91 octane is going to seriously restrict things
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Yes, I know, and that is why I was asking. 91 is the highest readily available pump gas I can get where I live, a few stations have 93, but that would be the highest I can get here, and I just want to be able to use what's available for convenience.
The car, with only a cold air intake and straight pipe header-back exhaust (with (high-flow) converter - mandatory on the street), puts out 135hp (& 133 ft-lb trq) to the wheels (untuned) - this is with the stock rotating assembly. I'm wanting to get 300hp at the wheels with the fine tuned intercooled turbo setup.
Any idea on how much boost I would need (turbo setup is rated to max out at 450hp), and if the amount of boost is possible on 91 octane?
I could setup a water injection system if necessary.
Thanks!
 
Switch to e-85. You should be able to run 20psi safely on a good tune. I'd keep it down to 10-15 though on 91 octane. on e-85, and a good intercooler, you could run 30psi. Or the water injection would be fine too, but if you ever run out of water, watch out!!

ever thought about a scramble boost function? you can have a lower amount of boost (10psi will probably get you pretty close to where you want to be. It'll feel good anyways...) and when you're feeling particularly froggy, you can turn on the scramble boost and, for a short time, you'll get a bigger (predetermined) amount of boost and fuel. That would serve to keep your fuel economy up, not wear on your internals too much, and give you an extra 50-100whp right when you need it.

PS: What about your block? You can have the most amazing internals on the planet, and they mean nothing if you blow a hole in your block. Titanium sleeves?
 
Sleeves are for high boost. I guess iron sleeves would work too. As long as they're stronger than aluminum. Is it a cast iron block? If so, then you prob don't need sleeves. Saturn tho, I was assuming aluminum. I guess I don't aim for a number. You prob don't need it for 300whp...

but if you're going to have more than 25-30psi, you prob need sleeves. 300whp is more like 350-360bhp If you decide you want more than 300 somewhere down the line, it may be a good idea...(on an aluminum block)
 
Yes, it is a "lost foam" cast aluminum block.
I actually have to travel about 100 miles or so to get e-85 (I live in one of the states that happens to not have it unfortunately) Could someone give me a decent whp estimate of 10 psi of boost on 91 octane with my setup (just a guess will do)? Also, I use octane booster before every fill-up but I count it out to keep my numbers conservative.
I was thinking, after I have the turbo all set up, if I want more power, to add a 50-100 hp shot of nitrous to at least give a faster spool up or enhance the curve. Would a 300whp intercooled turbo car + 100 shot of direct port nitrous need to be sleeved?
If I decide to expand my hp desires, I'll have a custom block made (cnc forged billet aluminum, which is stronger than cast iron) instead of just sleeving it.
Thanks for all the help this far tho! You guys are really great and fast responses, I love it!

Edit: Also, what would the differences be if I included a water injection system (just water not water/meth) on the 91 octane setup? vs non water cooled. Higher psi limits?
 
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Steel sleeves would be fine, I know loads of cars running up to 30psi on cast iron blocks without sleeves. Nothing wrong with overspeccing though. I myself am running 24psi and around 340fwhp on a standard cast iron block and 8:1 comp ratio. 2ltr 16v btw.
 
Not higher psi limits so to speak but better heat management which has a knock-on effect on a number of other factors which I can't go into ad I'm on my phone and it takes forever to type!
 
MasterAuron said:
Steel sleeves would be fine, I know loads of cars running up to 30psi on cast iron blocks without sleeves. Nothing wrong with overspeccing though. I myself am running 24psi and around 340fwhp on a standard cast iron block and 8:1 comp ratio. 2ltr 16v btw.
Click to expand...

What kind of fuel are you running?
 
I've just read about a guy running 25psi boost on a standard 10:1 CR with some carefully thought out engine management and fuelling upgrades! (Honda engine) so it does show that it is possible.

Have a peek at a new article I've done about lowering compression ratio for some more pointers in this area.
 
As good as possible ecu is the key. This will give you much better adjustment in all areas

I uprgraded my power fc to an HKs f con V pro gold - double the processing power but that gives four time more accurate adjustment for fuelling/timing etc. and you need that if you are running over 200bhp per litre !

This extra adjustment allows you to run much " closer to the line " because the map will have 4 squares to set a opposed to one with the above examples.
 
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As sleeper said, The tune is everything. You need strong materials partially because the tune is never going to be perfect. People never really take the tune seriously, but it's the difference betwen a 200whp car on 40psi, a 400whp car on 20 psi, and a pile of steaming scrap metal on the side of the road. The tune is EVERYTHING.


If you've got the money for a crazy build like this, why stop at 300 wheel? Certainly with the build you're doing you can stand to snake out at least 400-450 without a problem. Steel sleeves are going to be more than good enough for the build if you're not looking to make over 700whp. the rotating assembly and valvetrain you have picked out will hold waaaaaay more than 300whp and with sleeves, you're most likely going to get it. put on sleeves and you can probably run 40-50psi. You'll easily be over 500 wheel! BUT.....only if you get a good tune!

Steel sleeves if you want to go maybe 500-700whp, titanium sleeves if you want to go past that, or just get your billy bada-- block.

If you want a guess about 10psi on your build, I'm thinking around 220-230whp. kind of a sad number for the amount of work you have done. if you want to run about 20psi, you'll probably hit your magic 300 number. You may be ok at this amount, but speed is addictive. for people like us, it's our drug of choice. May as well be safe while you have the chance. Then it's just fun!
 
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kain35m said:
As sleeper said, The tune is everything. You need strong materials partially because the tune is never going to be perfect. People never really take the tune seriously, but it's the difference betwen a 200whp car on 40psi, a 400whp car on 20 psi, and a pile of steaming scrap metal on the side of the road. The tune is EVERYTHING.


If you've got the money for a crazy build like this, why stop at 300 wheel? Certainly with the build you're doing you can stand to snake out at least 400-450 without a problem. Steel sleeves are going to be more than good enough for the build if you're not looking to make over 700whp. the rotating assembly and valvetrain you have picked out will hold waaaaaay more than 300whp and with sleeves, you're most likely going to get it. put on sleeves and you can probably run 40-50psi. You'll easily be over 500 wheel! BUT.....only if you get a good tune!

Steel sleeves if you want to go maybe 500-700whp, titanium sleeves if you want to go past that, or just get your billy bada-- block.

If you want a guess about 10psi on your build, I'm thinking around 220-230whp. kind of a sad number for the amount of work you have done. if you want to run about 20psi, you'll probably hit your magic 300 number. You may be ok at this amount, but speed is addictive. for people like us, it's our drug of choice. May as well be safe while you have the chance. Then it's just fun!
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Thank you very much. I will probably go for the steel sleeves on my current setup. I will be starting out at 10psi (that's just my minimum starting point), see what results I get (I have a friend whose brother owns a shop and he will be helping me with the tuning) then up it from there. I'm only limiting myself to the 91 octane (for now, to have a super fun street car). I may go as high as 30 psi (in the end), but I wouldn't want to go past that (above 20, and I'd make it a sweet weekend drag car). Also, keep in mind that I am wanting to put direct port nitrous (Starting with 50 hp shot) on top of the turbo. So, easy 250+ (maybe even 300) on juice.
Right now I just want something streetable that can surprise the show-offs in their parents' stock camaro.
But like I said I'll up it from there once I get the tuning down and feel the need for more power. Who knows, I may have a 30psi turbo + 100 hp shot of nitrous running water/meth injection on gasoline/methanol blend or even straight meth drag car one day, lol.

Edit: most likely I'll end up with 20 psi, 100 hp nitrous, water/meth injection, and the billet block, and keep it on the 91 (or 93) octane with octane booster before every fill-up (the octane booster I use (STP) has nitromethane "jet fuel" in it, not sure how much).
 
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you can probably do without the octane booster. I doubt it's doing anything for you. If you really want an octane boost, find a sunoco around you and throw in a gallon of 100 octane. it's $7 a gallon and wil actually make a real difference. Oh, and by the way, speaking of 100 octane, my boss has a SC viper and he has a second tank that kicks in with 100 octane once he goes past a certain throttle position. (3/4, I think) That will help too. And remember what I said about a low boost/high boost setup (scramble boost) for when you need some extra power, so you don't always have to go get a "track tune" when you want to beat on it at the track. you can combine that Idea with the extra tank idea so when you hit the button, you get 5psi more boost, more timing, more fuel, and activate the 100 octane. It'll be as good as nitrous without anyone calling you a cheater :)

BTW, I'm pretty devious when it comes to speed/horsepower. If anyone ever gave me money enough to do it, I'd build a car that would blow your mind....Just sayin'....
 
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kain35m said:
you can probably do without the octane booster. I doubt it's doing anything for you. If you really want an octane boost, find a sunoco around you and throw in a gallon of 100 octane. it's $7 a gallon and wil actually make a real difference. Oh, and by the way, speaking of 100 octane, my boss has a SC viper and he has a second tank that kicks in with 100 octane once he goes past a certain throttle position. (3/4, I think) That will help too. And remember what I said about a low boost/high boost setup (scramble boost) for when you need some extra power, so you don't always have to go get a "track tune" when you want to beat on it at the track. you can combine that Idea with the extra tank idea so when you hit the button, you get 5psi more boost, more timing, more fuel, and activate the 100 octane. It'll be as good as nitrous without anyone calling you a cheater :)

BTW, I'm pretty devious when it comes to speed/horsepower. If anyone ever gave me money enough to do it, I'd build a car that would blow your mind....Just sayin'....
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Cool! (hmmm... Scramble boost + nitrous and 100 octane?) :bigsmile:
I knew a guy who had a spare tank in the trunk that switched from 100 octane to methanol with 10% nitromethane when he put the throttle all the way open. Naturally aspirated and very tuned. Was in a 70's muscle car like a charger or a chevelle.
 
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Just a note

The HE did stand for high efficiecy as in fuel burning . Ridiculous maybe but it was meant in relative terms to the very first V12 XJS's
It reffered to the redesigned combustion chamber as the head was prety much the only difference between the motors.
Funnily enough the early engines were a fair bit quicker
 
Re the scramble boost
Another way is to get a decent boost controller with enough modes and a remote switching system

My preference is a greddy profec b mainly because you can get a wireless button that fits on the steering wheel and engages high boost instantly. Fitted right and you can activate it without even taking your hands off the steering wheel.
After all its no good looking and/or fiddling around for a switch on the dash when you want another 80hp NOW
 
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