What's the highest compression that you guys run in your daily driver without detonating under most driving conditions, especially under acceleration on super unleaded.

I am thinking of doing 13.5 to 1 on the streets with 85mm Endyn 13+ to 1 rollerwave pistons.

 

your sig says your in cali, so the highest octane available pump gas is 91. 13.5:1 is definately too much for daily driving, plus with the summer coming up as well. id say 11.8-12.0 would be the upper limit on compression on 91 octane and w/o getting on the acfcelerator.

 

12:1 for 91 octane
13:1 for 93 octane

anything higher than 13:1 is high *** compression

 

Yeah, the oil companies are ripping us off here in LA. All of the sudden all super became 91.

 

Damn that's some high *** compression. And I thought I was pushing it with 12.5:1 on 93 daily driven.

I would definitely not run that on 91, not even 93 unless you buy some octane boost or something.

 

Yeah, Rick at Endyn said they run higher than 14 to 1 on their street motors but I wasn't sure what kind of gas they were running.

Texas mostly likely has better gas than California.

Anyways, hi-compression is good stuff if it doesn't not detonate. I've always been able to run bigger cams (non-vtec) with higher compression.

 

With that high of compression your going to be launching at 3000 rpms to go to the grocery store.

 

I don't want to sound negative, but the horsepower difference between 11:1 and 13:1 is like a mere 5-8 horsepower, unless you are going all out race and have crazy *** cams and bad *** valve train then it will show a significant hp increase. 5-8 hp on a car that already has 175 hp at the wheel is nothing you can really tell. Save yourself the trouble of having to try and find something like 96 octane to keep your engine from clicking. Check this page out http://www.bgsoflex.com/auto.html

 

I am in the 12:8:1 neighborhood on 91 and I can tell you that my car pings so bad you can hear it 3 blocks away!!!!!!!! I will trust what the people at JE told me today stick with 11:5:1 for 91 octane street, I figure JE would know somethings about compression

 

well thats a hard qustion to answer.
there are many ways to help detonation.
one way to help detonation is cooling down the water temp. wich thereby cools down the whole motor. (combustion chamber mostly)
this can be done by a bigger radiator or more efficent.
bigger water pump, a lower pressure radiator cap and lower temp thermostat, or even cutting small holes in it.
then the other way to help detonation is to run the correct a/f ratio.
but to answer the question 12.5 i feel is high enough for daily driving.

 

I disagree... The difference between a JDM gsr engine and a USDM gsr engine is .5 points higher CR. 10.1:1 to 10.6:1 and the JDM one is rated at 180 at the flywheel as opposed to 170 like the USDM one. Now i certainly dont expect to gain 20 flywheel hp for each point i raise my CR, but 5-8 for 2 points seems quite a bit low to me. Just my $.02

-Nick-

 

i guess the keyword here is daily drivable. running really high compression for about 5-10 extra horses isnt really worth IMO for daily driving. the summer is coming up and you enver know when you might get a bad tank of gas as well. changing headgaskets often is very fun.

 

If you are going to run high compression, upgrade your cams to take advantage of the high CR. Cams with big overlap will also help to reduce detonation by lowering combustion chamber pressures. Toda B's or C's, Skunk2 stage 2 or 3, Jun3's are all good choices for high CR motors. Then get some cam gears and tune it!

 

its not just peak power.
its power under the curve

so gains are everywhere on your powerband.

 

I am not looking for more peak power with higher compression. I am looking for what I call TORQUE REACTION. Peak power is more a function of engine breathabiltiy.

With higher compression the engine:

Sucks in air harder
Blows out exhaust harder
Has less intake dilution becuase there is less burnt gases in the combustion space

All this makes engines have more TORQUE REACTION or punchiness.

I think all of you guys have experienced this where there are some engines pack more punch and most of these "punchy" engines have more compression.

I wanted to see if I could verify Ricks claims at Endyn that there are people running 14+ to 1 compression on the street. I am building a 2.0L Vtec w/ Type R cams for a friend and wanted to see if it was safe to go above 12.5.

Thanks for the responses.

 

Ya you can run 14.1 on the street if you buy 55 gallon drums of race fuel like 100 +

 

Hell, yeah. I should open up a gas station and sell VP 112 octane and have a bunch of pimp Hondas and old school detroit iron and Hot VW's come by and kick it and fill'er up.

 

Quote:
I disagree... The difference between a JDM gsr engine and a USDM gsr engine is .5 points higher CR. 10.1:1 to 10.6:1 and the JDM one is rated at 180 at the flywheel as opposed to 170 like the USDM one. Now i certainly dont expect to gain 20 flywheel hp for each point i raise my CR, but 5-8 for 2 points seems quite a bit low to me. Just my $.02
__________________________________________________ __________________


The JDM has larger cams and may be rated 180 hp at the flywheel, but if you put a USDM and a JDM GSR motor on a dyno side by side...you won't see any difference...they are practically the same. It's the same thing with the civic si and the gsr...the civic is rated at 160 and the gsr 170, but once again, you put them on a dyno and they come out with the same numbers if they are completely stock (usually 143-146 at the wheel). I live a about 10 minutes away from 2 seperate dynos both of which had a free dyno day. I sat through about 30 dynos from everything like a stock 93 Civic hatch with the D16z to a 643 hp CRX built by JG and there were plenty of GSR's and plenty of 92-99 civics with B16a's, B18b's and B18c from both japan and our local junkyard and everyones numbers were turning out close to the same...so don't believe everything that you read.


[Modified by 2litreLsVtec, 7:34 PM 5/2/2002]

 

Interesting that 99 SI and GSR's perform the same on the dyno. I used to pull on HB's with B16A's all day with my 4dr GSR. Peak HP dyno numbers are not that meaningful to me.

 

Well if you are pulling on hatch's with a 4dr GSR it is not stock.
I can keep up with 2dr GSR's in my 98 HB with b16a, only mods are LSD, Flywheel, Clutch and Intake and exhaust. So especially if it is a 92-93 cx, vx, or dx they should be able to pull on you. Yea you may have 10 more HP and 15 lbs of trq but your car also weighs about 800lbs more. Just My $.02


[Modified by 98EK4, 11:56 AM 5/2/2002]

 

a guy near me (metro Detroit, MI) runs 14.7:1 84.5mm endyn rws in crvtec on 94oct, crower 63403 cams, hondata tuned (spark 12 deg BTDC); dunno if he has fluidyne or similar radiator, but he doesn't knock or ping.

 

Cool SloFu. That's what I was looking for.

98EK4, I know there are lot of fast B16A's out there. No doubt. For some reason the ones I ran on the freeway weren't so hot.

 

12.5:1- Is the highest compression ratio you can go on pump gas.

Here is a link that explains it in detail.
http://www.speedomotive.com/Building%20Tips.htm

 

I am not looking for a rule, I am looking for actual cases.

That's a pimp page though with good info. Thanks

 

Rocket, I'd be willing to bet that this person is running a Larry special and not something he built himself... it's not always what components and "known rules" you use to put something together... sometimes it's the techniques used for "fit" and "finish" that allow someone to unconventionally tune the "impossible"... If you really want to go there... you know who you really need to talk to...