highest street compression?

[sweet97]

A higher compression motor should rev quicker producing more gas volume and greater velocity. More boost will produce more power than compression so the point where compresion becomes a hinderance to power is important. 8.5:1 seems to be the consensus as to the best overall compression ratio for street use. Precision turbo has some interesting inf on compression vs. boost. mark

 

[swordfish]

My newest 2.4L is 10.0:1 and I love it. Just have to take it easy on the timing. And yes, its still a daily driver.

jeff

 

[1fast97gsx]

How does more compression produce more exhaust gas?

talonted_one: How is tuning a high c/r engine different than a low c/r engine, other than the fact you can't run as much boost?

low compression cars tuning does have to be perfect for it to run fine and safe ... high compression if you are a tad too lean you are screwed.

 

[Black94TSI]

How does more compression produce more exhaust gas?

talonted_one: How is tuning a high c/r engine different than a low c/r engine, other than the fact you can't run as much boost?

Well, not exhaust gas but exhaust energy. Makes sense to me, you burn more fuel because you're making more power with the higher compression, so there is more energy produced during combustion, and a greater amount of energy is expelled through the exhaust.

Swordfish, what octane of pump gas do you get, and how much boost have you been able to run on a 10:1 motor? High compression turbocharging seems to be the fad with Hondas right now, a lot of people are running 9.8:1, 10:1, and even 10.5:1 compression on motors built for their turbo setups, which has always seemed odd to me for a street car.

 

[swordfish]

I can run on 91 with no problems at 14 psi but I dont run much total timing (12-13 degrees total timing). We also have 101 at local pumps so I fill up with that sometimes as well. I can run up to 25 psi with about 18 degrees of total timing. Now that I am working out of a shop with a dyno I have lots of time to play around with the car for free. The car makes ~ 400whp on 91 @ 15 psi and 12 degrees total timing.

It needs a bigger hotside on the turbo now, that's for sure.

jeff

 

[1fast97gsx]

I can run on 91 with no problems at 14 psi but I dont run much total timing (12-13 degrees total timing). We also have 101 at local pumps so I fill up with that sometimes as well. I can run up to 25 psi with about 18 degrees of total timing. Now that I am working out of a shop with a dyno I have lots of time to play around with the car for free. The car makes ~ 400whp on 91 @ 15 psi and 12 degrees total timing.

It needs a bigger hotside on the turbo now, that's for sure.

jeff

Very impressive man. How much did you end up spending to do a 2.4 swap ... where did you get the motor and what car was it originally out of? I may be considering this or a 2.3...

 

[swordfish]

It didnt cost as much as some might think. The block and crank are a G64B that Polk had at his shop when I got ready to build this. I purchased the Ross pistons and 156mm Pauter rods from Marco and I had the head, cams, DSMLink and most of the other stuff left over from the dead 7 bolt. The first 2.4 I did earlier this year was a 9.0:1 setup and was very street friendly.

Then we had some flash flooding near my house and I had a hydrolock incident that ended in one bent wrist pin. The Pauters held up fine as did 3 of the pistons. So I called Marco for some more pistons. He says all he has in stock is a set of .080 over 10.0:1 pistons for his race car. I've always wanted to try a 10.0:1 setup so I took them.

The setup is a little tricky to tune because basically everything you know about DSM's and timing goes out the window. The fuel tuning is pretty much the same but you have to be careful with the timing. Plus BR8ES plugs are the standard. BR9ES at the track sometimes.

The red car is a 2.3L (8.8:1 JE/Eagle) and I really cant tell much difference between it and the old 9.0:1 2.4L off boost. The 2.4 sounds a little different because of the long rods but otherwise its a wash. Now that we have a bigger turbo (T66 P Trim) on the 2.3 car we'll find out how it stacks up against the 61mm P trim on the 2.4 car.

More details on are my site if you're interested.
www.swordfishGSX.8m.com

jeff

 

[TurboGraphX]

Higher compression DOES NOT produce more exhaust gas. It DOES produce more exhaust pressure.... THIS is why it will spool a turbo faster.
you can run as high a compression ratio as you want along with as much boost pressue as you want, so long as you use proper tuning to control the knock. (and so long as your head gasket can take it)
I'm currently running a non turbo 2.3 stroker at 13.5:1 compression on 93 octane and driving it daily. Granted, there is no stock parts in this engine except for the block and the bare head.
Anyway, it can be done.... just make sure that you do the rest of what's needed to do it safely.
Ken <--- builder of high compression, forced induction, engines.

 

[Batboost]

This time around, i will be running Btween a 9:5-9:8 compression. Ill post video of the setup, and talk of how it runs daily.

 

[IPT]

I will just chime in on my experiences.

I went from stock 1G pistons to JE 9:1 in my 1G and it was jsut fine to drive.

In my 2G I have 9.5:1 JEs and I love to drive it around, because my HX 35 dosen't spool til around 3800 rpms, so the higher Compression makes the slower highway cruising much easier. The off boost response is much better also.

PS I usally run 93 octane and 18 psi of boost. Right around 12-15 degrees of timing on my 2G

 

[Mr.Tao]

Higher compression DOES NOT produce more exhaust gas. It DOES produce more exhaust pressure.... THIS is why it will spool a turbo faster.
you can run as high a compression ratio as you want along with as much boost pressue as you want, so long as you use proper tuning to control the knock. (and so long as your head gasket can take it)
I'm currently running a non turbo 2.3 stroker at 13.5:1 compression on 93 octane and driving it daily. Granted, there is no stock parts in this engine except for the block and the bare head.
Anyway, it can be done.... just make sure that you do the rest of what's needed to do it safely.
Ken <--- builder of high compression, forced induction, engines.

how is your N/A car running with that high of a compression?

 

[TurboGraphX]

how is your N/A car running with that high of a compression?

Actually it is running very well. Low end pull is very hard. Which is what I was after, low end and midrange power. I haven't made it to a dyno yet, there are none in my area, but everyone that has ridden in the car is totally surprised when i do a half or three- quarter throttle pull with them in the car. Just keep in mind though, this engine took over a year to build and over a year consulting with many different parts suppliers and builders before the build even started. Each part on this engine is there to compliment or help enhance every other part. The engine was built to extract as much as we could from a 2.3L without going forced induction. Forced Performance and Crower both helped me alot with ideas and spec. arrangments.
Soon, she will be ready for the dyno and i'll have numbers to post, but i will tell you this....
If I cruise in first at 10 MPH, then stomp the go pedel... She will light up both front tires and smoke them untill I snatch third gear. So,... traction is a BIG problem! But I have won a few bets doing this.
Ken

 

[uh-oh]

Look its all about ignition and fuel control....i currently have my track car running 10.5:1 compression and about 16psi of boost and a nitrous window switch setup to give me a 75 shot til 10psi of boost..and i have a EvoIII 16g....as long as you have to pull timing slightly as long as you tune a little rich you have no problems...also makes for a sick track car...basically i keep the same fuel settings and up the boost to 21psi on race gas....car MOVES..have no problems pulling low 11s or high 10s on slicks....but remember this is also a built 420a not 4g63 so im not too sure the design limitations of your motor

 

[n0va91TSI]

Anyone go the other way with this? Lower compression and moe fuel and boost? F**k streetability low end. When im about going fast my rpms never get below 3.5K (with power launch of course). Come on guys this is an AWD turbo car, only reason I would want low end is for daily crusing sub 3k rpm and who needs power for cruising. My car with horrible compression has way less low end then most ppls cars but the extra second it takes to get the rpms up or drop a gear to get the high boost going is seriously not a factor. All the serious drag guys run low compression and crazy high boost. Its all about high airflow and burning lots of fuel not high compression. If your car is lightened you dont need the torque to get you going. Not to mention i think first gear is geared too low anyway. Unless you wanna do awd burnouts or something i really dont see the appeal of high C/Rs, we dont drive a big heavy truck.

 

[TurboGraphX]

All the serious drag guys run low compression and crazy high boost. Its all about high airflow and burning lots of fuel not high compression. QUOTE]


Ummm,..... What?!?!?!? You mean the shade tree, take it to local track, run it in a couple by runs unless you just happen to line up beside someone, Then drive it back and fourth to work the rest of the week, kind of "serious drag guys... right?!?

Why don't you go look at the specs on the Sport Compact drag cars?!?!? 13:1 - 15:1, and some even higher than that, compression ratios. High compression does as much for top end power as it does for low end. Think of it this way.. the higher the C/R, the faster the air fuel mixture gets into the engine, the better it is burnt (it isn't rocket science to know that a dense, packed, mixture burns better and faster) and the faster the exhaust gets out. It increases the WHOLE intake, burn, exhaust system.
Ken

 

[1fast97gsx]

yea man there are absolutely no advantages to a low compression car except for the fact that its a hell of a lot easier to tune and you can run a little more boost. However a high compression car at 10 psi will pull a lot harder than a low compression car at 10 psi so you have to decide which way to go .. high boost, low compression, low boost, high compression, or somewhere in between which is what I'm looking for. Serious drag racers do high compression AND high boost.

 

[sweet97]

Pro drag racers run very low compression with turbo cars. As low as 5:1 static compression. 35 lbs. of boost would grenade a 9 or 10:1 compression motor.
In na motors a point of compression is worth about a 5% increase in power. So going from the common 8:1 to 10:1 compression is worth 10% power inrease. A turbo car at 10:1 can run 5-6 psi of boost. lowering that 10:1 to 8:1 allows about a conservative 15 psi increase in boost. That is MUCH more than 10%. I believe each bar doubles HP. A bar being 14.7 psi. Run a 7:1 compression and you could probably run 25 psi safely on pump.
I know this is going to cause an arguement so do a search on precision turbo engineering. They will tell you like it is. Mark

 

[14.5 drift]

Pro drag racers run very low compression with turbo cars. As low as 5:1 static compression. 35 lbs. of boost would grenade a 9 or 10:1 compression motor.
In na motors a point of compression is worth about a 5% increase in power. So going from the common 8:1 to 10:1 compression is worth 10% power inrease. A turbo car at 10:1 can run 5-6 psi of boost. lowering that 10:1 to 8:1 allows about a conservative 15 psi increase in boost. That is MUCH more than 10%. I believe each bar doubles HP. A bar being 14.7 psi. Run a 7:1 compression and you could probably run 25 psi safely on pump.
I know this is going to cause an arguement so do a search on precision turbo engineering. They will tell you like it is. Mark

your dead wrong. The fuel and ignition systems they use is what allows them to use very high compression ratio's.

 

[14.5 drift]

Pro drag racers run very low compression with turbo cars. As low as 5:1 static compression. 35 lbs. of boost would grenade a 9 or 10:1 compression motor.
In na motors a point of compression is worth about a 5% increase in power. So going from the common 8:1 to 10:1 compression is worth 10% power inrease. A turbo car at 10:1 can run 5-6 psi of boost. lowering that 10:1 to 8:1 allows about a conservative 15 psi increase in boost. That is MUCH more than 10%. I believe each bar doubles HP. A bar being 14.7 psi. Run a 7:1 compression and you could probably run 25 psi safely on pump.
I know this is going to cause an arguement so do a search on precision turbo engineering. They will tell you like it is. Mark

also, psi has absolutly nothing to do with how much power a car makes.

 

[sweet97]

I'm not wrong, Precision Turbo is. If boost has nothing, absolutly nothing to do with power why run a turbo at all? Boost increases the pressurein the cylinder, higher cylinder pressure and more power.

 

[Maglin]

I'm not wrong, Precision Turbo is. If boost has nothing, absolutly nothing to do with power why run a turbo at all? Boost increases the pressurein the cylinder, higher cylinder pressure and more power.

No not really. More air and fuel = more power. Pressure is a by product which is actually kind of bad as the higher the pressure the more heated the air gets and that is a Negitive force on HP. That is why 2 different turbo's at the same pressure say 15 psi make differnt power on the same car cause one heats up the air charge more than the other... ie.. 14b vs. a FP3065..

 

[sweet97]

That is true and factors are being plugged in to fit particular statemets. I will respectfully bow out with having a compression of approx. 8.5:1 for the street and lower for a full tilt race car, just my choice! mark

 

[14.5 drift]

I'm not sayin I am right, and on a side note, that was the classiest way ive ever seen some one avoid an arguement

Exvitirmini runs 9:1 compression on their 1600hp skyline, ive also seen other race equipped cars running the same. NHRA top fuel cars also use some thing like 13:1 compression systems too, but I could be wrong, just thought I read that some place

 

[Maglin]

All out Full Drag Cars use Pistons with Gas Ports and they do run a pretty high static CR.. It depends on the engine builder but I think I remember it being in the neighborhood of like 13:1 or 14:1... But this is buring Methanol on Large displacement engines with Lots of "boost"... Those 14-1 roosts blowers pump a crazy amount of air into those motors... I believe they are putting down like 8000 HP now... That is why you will see a drag car jump to one side on a misfire... Loosing 1000 HP in a very brief moment just throws them.. Thus they run duel CDI inginitons... But this is all out racing.. you can't run gas ported pistons on the street.. Well you can but your oil comsumption under vacumme will be insain...

So the question is not what is the highest CR we can use... But what is the most expensive fuel we are willing to pay for.. Methanol burns hella slow compaired to pump fuel... I'm surprised that no-one is using pure meth in a DSM for all out drag purposes.. Well I guess the Fire going through the Turbo would definitlly kill it's life but Man what a show that would be...

To clairify Sweet97 I wasn't jumping on you... I was just pointing out the cylinder pressure isn't HP entirely... It's a Cool cylender pressure and fuel that makes HP.. I'm a noob on the sceen of imports but not in the realm of high performance auto's... Only reason I bought a DSM was one it was hella cheap and 2 my current rod is getting like 7-9 mpg and at $2/gal I was really going broke just driving it to work... Now I'm totally into DSM's and my buddies that have 3rd gen RX-7 cept telling me to buy a real car... LoL... But since both of their rides now have blown motors I guess I have one up...

Edit: Don't hate on me for my spelling errors please.... I can't spell and I know it.. But at least I can read... All that matters... LoL

 

[1fast97gsx]

Pro drag racers run very low compression with turbo cars. As low as 5:1 static compression. 35 lbs. of boost would grenade a 9 or 10:1 compression motor.
In na motors a point of compression is worth about a 5% increase in power. So going from the common 8:1 to 10:1 compression is worth 10% power inrease. A turbo car at 10:1 can run 5-6 psi of boost. lowering that 10:1 to 8:1 allows about a conservative 15 psi increase in boost. That is MUCH more than 10%. I believe each bar doubles HP. A bar being 14.7 psi. Run a 7:1 compression and you could probably run 25 psi safely on pump.
I know this is going to cause an arguement so do a search on precision turbo engineering. They will tell you like it is. Mark

don't want the start an arguement but here is my take: Yes with lower compression you can run more boost. Yes on an NA car higher compression will make more power. Is this true on a turbo car? Yes. The ideal setup is high boost AND high compression which is what pro drag racers use. As far as searching for precision turbo / engine I have no need for that. I had a talk with patrick from pte about this exact thing a year ago. This was when I bought a fmic and scm61 turbo from them. I also got my injectors from them and a new exhaust side for the turbo ... so trust me I have talked to them more than once. His exact response was " A big turbo needs more boost to really make the power it can, however raising the compression of the motor and the same boost level it will make even more. "

To say that each bar doubles hp is just wrong. A 14b at 24 psi lets say will make 300+ hp. My turbo at 24 psi has but down 410 whp on the dyno ... so say 450 at the crank at least? How much hp a turbo will give you really depends on the size of the turbo and also the compression of the motor ... not just boost level. Of course cams and manifolds and so on affect it too but that's besides the point.