Can I run high ccompression AND boost?

[EODguy036]

wanting to use some wisco 11/1 compression pistons that are 90mm bore. goal whp is 350. my question is will the cylinder walls be able to take the abuse of boost and high compression if i bore that far.

[SR24DET]

Cast iron block

[480sx]

If your tune is spot on you'll be alright. 90mm bore is to thin for high HP apps IMO, but for 350 you should be fine.

[EODguy036]

yay!!!! that made my day. the tune is going to have to be precise, but im glad to know that 90mm is'nt too big.

[s14derrick]

11 to 1 comp ratio? isnt that horrible for boost?

[neverlift]

actually no!, BUT it does make tuning a little harder and the high risk of ringland failure is going to increase .. but as long as detonation is not going on he will be fine. Raised comp is more air to spool the turbo so its win win unless heat/detonation come into play.

in theory you could run w/ever comp and boost the crap out of it so long as the parts can handle it and the tuning/fueling is good.

I personally dont like the .030 over... but thats you choice

[EODguy036]

what dont you like about it, is that too far over? would i be puting my cylinger walls at risk for cracking? if so i may go 89.5mm

[WDRacing]

Just to toss out some facts...

More power is made per capita by lowering compression and increasing boost. That's from Kenne Bell himself.

Everything revolves around octane limitations, not what the motor will handle. The KA will make 700whp if you have the internals swapped out. Static compression has noting to do with when the parts will fail.

On an alcohol motor this is a great idea, on something that runs on pump gas, not at all.

[turbo2nr]

ive seen high comp. honda motors make more power on same boost levels as low comp. motors.

i think this is a good idea and i always wanted to do this, but i dont see it being realible or realistic after 400whp.

i say do it convert to e85, get a good standalone and make sure your tune is on point and you should be ok. the motor will be super responsive.

what size turbo do you plan on going with?

[compression]

Make sure you are tuned!that is key. Use a standalone that has datalogging and have a pro do it.You may have to run race gas if you end up boosting past the knock threshold of premium pump gas. E85 is also a good candidate (cheaper).

You can also have a meth nozzle spraying into the intake manifold when under boost to cool things down. it adds complication, but might be necessary as your need for "mo powa!" goes up.

High-compression + Boost = super fun and super fast.

[EODguy036]

right now i have an e-manage ultimate. but i want to go stand alone, not shure which one yet but thats for another thread. as for the turbo i am going to call borg warner and ask what would be best for the build im doing. sorta hard to get a hold of them on my scedual though.

knock threshold? im guna have to look that one up.

what does methanol do besides cool?

[neverlift]

meth is gonna help increase your knock resistance,

hey wd but does he say you will make less power with an increase in compression at the same boost? Highly doubtful but again any knock and your done.

As stated e85, and some 1000cc injectors would be awesome on this build!

knock threshold is when the fuel used can no longer resist knock, but let another more versed member chime in!

[C-Kwik]

An old friend of mine used to recommend getting your block sonically tested before boring to make sure it can handle it. The KA, being a sand cast block is subject to poor tolerances. It can be fine for the intended applications, but straying outside of that might mean you end up with a thin wall somewhere. This was KA specific advice that came from racing KA powered vehicles (GT3 class, IIRC).

While high compression and boost would be desirable from a theoretical standpoint, the biggest limitation, as others have mentioned, is the fuel Unless you have access to and are willing to pay for higher octane fuels that can handle the net heat and pressure that results from the higher compression coupled with the intended amount of boost, this may be way over your head. Frankly, if you're here asking these types of questions, you're probably not qualified to handle such a task. Could you do it? Maybe. But its going to be a big engineering challenge and the end result might be that you have to retard timing a lot or reduce dynamic compression (via valve actuation) to reduce the possibility oif detonation. Even if you can get it to run on pump gas, one bad batch of gas can ruin the motor. Bear in mind that automotive engineers don't employ this kind of "time bomb" when it comes to mass production.

Raised comp is more air to spool the turbo so its win win unless heat/detonation come into play.

Raising the compression does nothing to increase the volume or mass of air being pumped through a motor. The mass of air being pumped through a motor is tied in with displacement not compression ratio.

[neverlift]

I stand corrected. confused but corrected.

I love nico

[C-Kwik]

I stand corrected. confused but corrected.

Its not that confusing. Consider syringe attached to a coffee can. Both are sealed from the outside environment, but have a path to each other. Push on the syringe and the pressure will increase, but only be a small amount.

Now take the same syringe and attach it to a soda can in the same manner and push on the syringe. The amount of air injected into the soda can is the same amount as the put into the soda can. But the soda can will increase in pressure more as the volume of the can is smaller.

Since we are using the same syringe, the displacement is equal and moves the same amount of air. But the amount it compresses the air (pressure) is different. This is essentially the same concept. An engine's cylinder basically pushes a given amount of air into different sized combustion chambers to achieve different compression ratios. Hope that helps.

[EODguy036]

so what im hearing is in order for me to use my desired setup i would need to use a high octane fuel in order to prevent detonation. if this was a weekend car that would be fine, but as a dd that would be just plain inconvenient. 9.5/1 90mm may be a better way to go. though i would love to have that kind of throttle responce.

[WDRacing]

I've talked about doing this with a few other guys now. Very similar to your idea but using the KA24E pistons or rods or something. The end result is failrly high compression, like 10.5 or something. I'm not sure of the details really because I was always the voice of opposition.

Your next really important decision is now the turbo size. If throttle response is that important to you, I'll tell you right now you won't like lag. So you're not going to want a turbo with anything bigger then a .48AR exhaust housing unless it's a twin scroll unit, which are insanely expensive... On the other hand, with 350 as your power goal you don't need to use forged internals. The rest depends on mileage etc...

A great tune will improve your throttle response some btw.

WD

[neverlift]

thanks Cthat helps a ton.

wd I thought you ended up with something like 11.4:1 when using sohc pistons in a dohc motor? IDK it would be different for sure, what would a comp test look like on something that high? 250, more? I was shocked at the 212 my motor put down across the board.

[EODguy036]

i figured its got 140000+ miles so i might as well go ahead and put some new internals, and who knows what im going to want to do next.

with 10.5/1 plus boost could you run 93 pump gas?

ok so i understand knock resistance and octane a lot better now. but is there a way to know what static comression will need what fuel?

[WDRacing]

i figured its got 140000+ miles so i might as well go ahead and put some new internals, and who knows what im going to want to do next.

with 10.5/1 plus boost could you run 93 pump gas?

ok so i understand knock resistance and octane a lot better now. but is there a way to know what static comression will need what fuel?

There are only general rules. But here's a tip, no one raises compression when they add a turbo. 9.5:1 factory compression is actually more then I'd like to run.

Can you run 10.5:1 and boost? Sure you can, but you'll only be able to run a small amount of boost.

Can I ask why you're so stuck on high compression and boost? Everyone I can think of that has any type of high compression and boost does so only because they are using a factory block. Like Honda or Toyota...

The increase in compression isn't going to change the power band of the KA all that much. So why bother? If it turns out that you've built a knock monster you're simply screwed. Unless you rebuild the entire motor again.

WD

[EODguy036]

i want to use as little boost as posable to get the 350, high compression sounded like a good way to me. i was right in theiry, but failed to realise the need for a more knock resistent fuel. so i thank you guys for all your input, and i will be going with some wiseco 9/1 90mm pistons. hope i can show you all the finished product by next feb.