im rebuilding as some may know. i want to boost in the future probably next spring. so im going to be running n/a for awhile. im trying to get pistons now. and the question is i heard you want lower c/r for easy tuning. my set up plan is/was 10.5-1 pistons 086 head and w41 cams if i can find them. im asking you guys if you could maybe pick apart my set up and educate me on boosting with this set up or if its even smart to do so. and if w41s wont work then what cams should i look for? i still want power at a n/a state but still be able to boost without rebuilding the whole block again.
If you go low compression while you are n/a then its going to be dog @!#$ slow before any boost. The low compression is going to cause that. Im running stock compression and im glad I am. Even if I was to take the boost off, I would still not have lost all my down low power if I was n/a...
Back when SpeedRacer built his LD9 (low compression) it made 171(roughly) whp n/a. That is more than stock. So if it is built right, and tuned right it can still be good.
With that being said I'm a fan of slightly higher compression and boost.
FU Tuning
I too run higher compression (stock 10:1 but high for the amount of boost I run). It comes down to tuning capability in all actuality. For various reasons I remained at 10:1 but the biggest reason was to maintain power and gas mileage while off boost. My setup allows me to basically have two cars in one since I run several systems, most of which remain asleep until atmospheric pressure arrives. The higher compression ratio while using F/I is mostly a factor of cylinder pressures and your ability to keep them under control while hitting peak TQ (a sign of peak cylinder pressure). If you have the ability to retard your timing as you reach this area of pressure to help ease the shock load and then gradually begin adding timing back in you will be fine with high c/r. This requires the ability to have various timing retard capabilities which in our case can be limited depending on what you have. When it all boils down the lower compression is slightly easier for tuning simply because you have a little more padding/safety net. You can also typically run much higher boost pressures with less of a worry about spiking cylinder pressures as seen in higher c/r which in turns removes that from the equation when accounting for tuning. All in all either way is fine and in your case so long as you feel comfortable tuning your setup (or find someone that does) then stick with the higher compression so you can drive N/A for as long as you wish while keeping all the characteristics of your normal setup.
ASE Master Certified Automotive Technician
Addicted to meth wrote:Back when SpeedRacer built his LD9 (low compression) it made 171(roughly) whp n/a. That is more than stock. So if it is built right, and tuned right it can still be good.
With that being said I'm a fan of slightly higher compression and boost.
Brian was the first person that came to my mind, too. IIRC, he was also only running a 95 intake cam with a HO exhaust cam.
I have no signiture
That's another question. Are w41 cams safe with boost? Or what cams are good?
I plan to run around 10:1 and about 15psi from a t04e 57 trim Turbo. The higher compression definitely helps with low end when out of boost.
"Oil Leak ? What oil Leak ? Oh, Thats Just The Sweat From All The HorsePower!!"
I'm looking at a garret 57 trim .60a/r I want a electronic boost controller. Since I'm going forged pistons and rods i might peak at 20psi? But cruise way lower.
96-Z.24 wrote:I'm looking at a garret 57 trim .60a/r I want a electronic boost controller. Since I'm going forged pistons and rods i might peak at 20psi? But cruise way lower.
I would probably limit your c/r to 10:1 instead of 10.5:1 and remain with your 20ish psi. You will definitely want to run methanol unless you like paying $10+ a gallon for race fuel. You could go higher in boost but you will want to look into another ignition system at that point and then you will also REALLY be relying on methanol which can be a recipe for disaster. Unless of course you have any number of safe guards available in place to prevent such disaster should something go awry.
ASE Master Certified Automotive Technician
What about cams? Are any cams okay with boost as long as you tune with them in mind?
96-Z.24 wrote:Are any cams okay with boost as long as you tune with them in mind?
Pretty much yes, the benefit of cams designed with f/i in mind are those that compliment forced induction. To maximize performance you want each part to properly compliment the next and cams can in a lot ways be the heart of the system in regard to how the engine breaths. Just depends what you want to be able to do. Just remember that cams are a permanent alteration to the equation unless you have adjustable timing gears, then you have some play with certain aspects of breathing characteristics. The discussion of cams is really a whole separate discussion that can get very complicated and detailed quickly if you are not comfortable in your understanding of cam profiles.
ASE Master Certified Automotive Technician
I have a bassic understanding of cams. I don't want to get a custom grind. Just looking at the secret cams, ho, or w41. Any of them would benefit me n/a but f/i I know is a diffrent story. Do I need to make a new thread asking about them?
The W41s should be fine with boost. While they are aggressive compared to the stock cam profile they are not so aggressive that they will hinder boost. They still don't have a ton of overlap, which is what hurts boost, because of reversion.
Awesome. So w41s and 10.1 c/r is fine.
