Before people start having a heart attack, i'm well aware that optimal safe compression would be in the 9.5:1 - 10.5:1 range but i'm kinda falling in to a really good deal on a dart motor that was setup as a 2.0 liter 11.5:1 compression.

This motor has never been ran before so i know i could just tear it down & thow different pistons in it but it's exreamly temping to run it as is. I'm in search of about 400-500hp, i wanna run low 11's high 10's in my 95 civic coupe.


Modified by Running925 at 4:01 PM 12/27/2007

 

11.5:1 and up id say is close to a no no

 

i would change the pistons for that power goal.

 

When an engine has higher static compression, it means that you will have to run a higher fuel grade earlier than a car with lower static compression. If you dont have a problem driving around on 110 octane or C16 race gas, you could meet your goal. If you want to do something practical, i would lower the compression and continue on with your build. It will cost a lot more in the long run to run high octane fuel w/ high compression than it would to sell the high compression and run something like a 9:1 compression.

 

well if i were to sell the pistons i'd probably end up going 10.5:1 as next option on the wiseco list is 8.8:1 & thats not happening!

I drive the car in the evenings & on the weekends, i race at the local drag strip maybe 6 or 7 times per summer.

currently have a forged ls motor with 9.5:1 compression & it's ran really well for me. I'm just wanting to move up to something a little more powerful. Going with a 2.0 Dart block & a GSR head thats been worked over by import builders. The turbo i'm planning to use a little longer is a garrett t3/t4 (.60/.63).

 

i think the b18c5 is ~10.7:1 ... and premade kits usually suggest really low boost for that application (6 - 9 psi) i would just go with low compression pistons so you can actually make use of a turbo system that dart motor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Running925 &raquo;</TD></TR><TR><TD CLASS="quote">well if i were to sell the pistons i'd probably end up going 10.5:1 as next option on the wiseco list is 8.8:1 & thats not happening!
(.60/.63).</TD></TR></TABLE>

whats wrong with 8.8:1? im 8.3:1 and i freakin LOVE it! 333whp and 260tq at 12psi (gt3076r) on 91 octane, and i can go up to 20 psi on 91 octane!! the only thing with compression that low is that it NEEDS boost to move, im turning mine back up to 15psi, thats where it was REALLY happy

i made 317whp and 240tq on the same setup with a t3/t04e at 15psi.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">

whats wrong with 8.8:1? im 8.3:1 and i freakin LOVE it! 333whp and 260tq at 12psi (gt3076r) on 91 octane, and i can go up to 20 psi on 91 octane!! the only thing with compression that low is that it NEEDS boost to move, im turning mine back up to 15psi, thats where it was REALLY happy

i made 317whp and 240tq on the same setup with a t3/t04e at 15psi. </TD></TR></TABLE>

problem with that is i want a little bit of off-boost power. Please don't take offence to this but don't want the car to feel gutless when the turbo isn't spooled. I've had a few very low compression motors with big turbo's on them & they take for ever to spool & until you do, your loosing the race if you know what i mean.

 

I get scared as **** reading these types of threads because I'm going to be boosting my 06 RSX and it's already 11:1 CR... I really don't want to frag a motor that has less than 15k miles on it!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Running925 &raquo;</TD></TR><TR><TD CLASS="quote">

problem with that is i want a little bit of off-boost power. Please don't take offence to this but don't want the car to feel gutless when the turbo isn't spooled. I've had a few very low compression motors with big turbo's on them & they take for ever to spool & until you do, your loosing the race if you know what i mean.</TD></TR></TABLE>

a stock LS is 9.2:1 and they aren't all that bad so the 8.8:1 will be ok, just run aggressive timing down low if you can and that would help a ton. I'm with ya though i used the Wiseco 9.7-10.2:1 pistons but im not trying for 500whp.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blinx9900 &raquo;</TD></TR><TR><TD CLASS="quote">

whats wrong with 8.8:1? im 8.3:1 and i freakin LOVE it! 333whp and 260tq at 12psi (gt3076r) on 91 octane, and i can go up to 20 psi on 91 octane!! the only thing with compression that low is that it NEEDS boost to move, im turning mine back up to 15psi, thats where it was REALLY happy

i made 317whp and 240tq on the same setup with a t3/t04e at 15psi. </TD></TR></TABLE>

I prefer 9:1 or less on a street car that's primarily going to run on pump gas. The difference in the knock limit is huge.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Running925 &raquo;</TD></TR><TR><TD CLASS="quote">

I've had a few very low compression motors with big turbo's on them & they take for ever to spool & until you do, your loosing the race if you know what i mean.</TD></TR></TABLE>

You should look into a car with a transmission, it allows you to change the ratio between engine speed and wheel speed so you can achieve different rpms at a given speed. Makes a world of difference when racing a turbocharged 4 cylinder!

 

you could run safely abt 350-400 taking it to the right tuner. anything after that i would use some type of race gas or look into using E85. there was a guy around here he boosted his motor at 11.5 and he made like 380 for the longest time

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">
You should look into a car with a transmission, it allows you to change the ratio between engine speed and wheel speed so you can achieve different rpms at a given speed. Makes a world of difference when racing a turbocharged 4 cylinder! </TD></TR></TABLE>

LOL nice!

Yea i might go with the 8.8's & then have the thing decked or go with a different rod so that i can get the motor to about 9.5:1 like my current LS motor. I guess it would be safter for a pump gas car. I'm just tryin to make sure that the car is faster in the end. This is a lot of time & money spent to do this as most of you know & i just wanna make sure it's right.

I'll have to post up the build specs & parts list in a thread on here soon so that i can get a little more input.

 

Use the turbo to get the power, no sense limiting yourself to 15psi on pump gas when you can run 20+ on pump gas at lower compression and be safer.

There's a reason every OEM turbo car is low compression...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tony1 &raquo;</TD></TR><TR><TD CLASS="quote">Use the turbo to get the power, no sense limiting yourself to 15psi on pump gas when you can run 20+ on pump gas at lower compression and be safer.

There's a reason every OEM turbo car is low compression...</TD></TR></TABLE>

thanks for your input, it's greatly appreciated.

 

I'm surprised nobody said run 93 oct and meth injection on that high cr motor

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ghostofnyc &raquo;</TD></TR><TR><TD CLASS="quote">I'm surprised nobody said run 93 oct and meth injection on that high cr motor</TD></TR></TABLE>
because bandaides aren't solid state like compression is.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ghostofnyc &raquo;</TD></TR><TR><TD CLASS="quote">I'm surprised nobody said run 93 oct and meth injection on that high cr motor</TD></TR></TABLE>

I certainly think that is a viable solution...

11.5 isnt too scary IMO...but shooting for 500 hp, you are def going to need to run higher octane fuel.

If you have E85 in your area...you have a fighting chance with just pump fuel at 11.5:1

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Running925 &raquo;</TD></TR><TR><TD CLASS="quote">I'm in search of about 400-500hp, i wanna run low 11's high 10's in my 95 civic coupe.


</TD></TR></TABLE>

400-500 WHP, better stay around 9.5:1 on 93 oct, or even lower if you run on 91 oct.

I am at 10.5:1 right now at 380 WHP, but I get 94oct here at the pumps, and I am on an AEM EMS with my water/meth injection integrated with the EMS with a bunch of fail-safes.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Tony the Tiger &raquo;</TD></TR><TR><TD CLASS="quote">

400-500 WHP, better stay around 9.5:1 on 93 oct, or even lower if you run on 91 oct.

I am at 10.5:1 right now at 380 WHP, but I get 94oct here at the pumps, and I am on an AEM EMS with my water/meth injection integrated with the EMS with a bunch of fail-safes.</TD></TR></TABLE>

can you elaborate on your fail-safes

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ghostofnyc &raquo;</TD></TR><TR><TD CLASS="quote">

can you elaborate on your fail-safes</TD></TR></TABLE>

Pressure sensor for water/meth injection pump and lines and inputs signals into the AEM. There are tons of configurable inputs and outputs to tell the AEM to switch maps, dump fuel or trim timing when pressure readings are low or non-existent. Reservoir level sensor that triggers an LED on my dash if it's low, and this light also sends a signal to the AEM to run my non-meth maps. AFR sensor reading inputs to the AEM's configurable outputs to turn on my secondary nozzle and kill timing (in case of fuel pump failure, etc) if my AFR's are ever leaner than 12.5:1 AF under 80+ % throttle, more than 16 PSI and above 5000RPM.. and so forth.