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**DONOTDELETE**
10-30-2001, 08:06 PM
I want to raise my compression ratio on the ka24de, 9.2:1 (i think it is) to 10.2 - 10.5 can someone give me the best methods on reaching this goal and how much hp gain it would give me.

Meeks32
10-30-2001, 09:02 PM
The only way I know is to swap pistons, I heard that if you shave the head on a OHC engine that it will mess up the timing. I dunno, you could probably see 15hp if you raise it to that, I may be wrong though.

**DONOTDELETE**
10-30-2001, 09:12 PM
You can shave the head on an OHC engine. Or even easier, just get a thinner head gasket. I know they do it with Honda's. I'm not really sure what steps you have to take not to screw up the timing. I'd guess adjust the belt tensioner, and maybe get some adjustable gears(which wouldn't be a bad idea anyway in order to get the most out of that higher compression, and avoid detonation).

**DONOTDELETE**
10-31-2001, 06:46 AM
<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by Strider:
I want to raise my compression ratio on the ka24de, 9.2:1 (i think it is) to 10.2 - 10.5 can someone give me the best methods on reaching this goal and how much hp gain it would give me.<HR></BLOCKQUOTE>
Have different Pistons Installed. Stiffer Valve springs. Shaving the head without reworking the Cams or gears will cause trouble.
If it is just HP that is being looked for, have the Head ported, port match the intake and exhaust and angle the Valves.
A good 10HP can be realized from this and still pass smog.


http://www.freshalloy.com/

ADAM HUTCHINSON
10-31-2001, 11:24 AM
approx every point in compression raised will get you 10% more power..until you reach 15:1...then it drops off by alot

so lets say you have 125bhp...you will end up with 137bhp..not much of an increase for the hassle of ripping pistons out http://www.freshalloy.com/

TURBO TURBO...i hear them chant

primeral
11-01-2001, 12:31 AM
Some types of headwork changes the combustion chamber volume, therefore altering the compression ratio. If you are having headwork done, do it before ordering your custom pistons.

**DONOTDELETE**
11-02-2001, 03:49 PM
change the pistons. If you shave the head, you will end up retarding the cam timing unless you can get an adjustable cam gear. Do they make em? I know nismo has a gear with various bushings but i think that an adjustable would be great....oh wait, im talkin sohc. never mind about the thinner gasket unless you get a good solid gasket like copper or maybe some of those performance fel pro.

**DONOTDELETE**
11-02-2001, 03:52 PM
btw, i think that it should give you more than 2.5horses per cyl.

**DONOTDELETE**
11-02-2001, 07:07 PM
<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by 240hp:
btw, i think that it should give you more than 2.5horses per cyl.<HR></BLOCKQUOTE>
Correct,
I should have clarified that the Head work and match porting will get approx. 10HP to the rears and with the compression increase will add approx. another 6 - to the rears.
Which makes it about 34-38HP at the Crank, with $1350 input.

http://www.freshalloy.com/

Meeks32
11-02-2001, 09:26 PM
Help explain this to me guys, but why do you lose more & more hp through the drive train the more hp you have? Our cars have about 125-130 whp right? & 155 at the crank. So im losing about 25-30 hp. If my engine was making 500hp your saying that im going to lose 100hp, I dont get it.

**DONOTDELETE**
11-02-2001, 09:45 PM
<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by Meeks32:
Help explain this to me guys, but why do you lose more & more hp through the drive train the more hp you have? Our cars have about 125-130 whp right? & 155 at the crank. So im losing about 25-30 hp. If my engine was making 500hp your saying that im going to lose 100hp, I dont get it.<HR></BLOCKQUOTE>

This is because of the drivetrain loss that FR (front mounted, rear wheel drive) have. Only a percentage of the power at the flywheel is actually getting to wheels. The loss is approximately 15-20%, depending on efficiency. If you don't like it, you can always get an MR or FF car.

-sherwin

**DONOTDELETE**
11-02-2001, 11:07 PM
anyone know if there is a thicker gasket out there that we can use to decrease our CR, I know a lot of other engines have them, but seeing how our KA is a bastard engine you never know

Meeks32
11-03-2001, 12:08 AM
I dont think you got what I was trying to ask. Im not complaining about the extra loss of the FR layout, I was just trying to understand why you dont lose the same amount of hp no matter how much hp the engine makes. Maybe I just need to major in engineering so I can learn this stuff.

**DONOTDELETE**
11-03-2001, 04:30 AM
Idont think thats true about the more horspwr you have the more drvtrn loss. If i had a 65lb rim and it takes (?) hrspwr to turn it to 7000rpm, it will not cost more hrspwr if i made(?plus?) to spin it to 7000rpm.

T%here are some custom copper gaskets that have thkness upon request(and its not like you can order a 1/4inch gasket) but you will have to do oyour homeworke and calculate. I dont think thats the right way to go to drop comp and I dont really know how much youd drop. There are formulas out there.... do your homework.

Mav1178
11-03-2001, 04:33 AM
<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by Meeks32:
I dont think you got what I was trying to ask. Im not complaining about the extra loss of the FR layout, I was just trying to understand why you dont lose the same amount of hp no matter how much hp the engine makes. Maybe I just need to major in engineering so I can learn this stuff.<HR></BLOCKQUOTE>

Frictional force is an equation of the coefficient of friction times the normal force of the object applied to the frictional surface in question. As the normal force of the object increases, so does the frictional force assuming the coefficient of friction is the same.

If you apply this concept to a car, you'll find that a high HP car will lose more horsepower to drivetrain losses, but the % is the same.

-alex

[ 11-03-2001: Message edited by: Mav1178 ]

**DONOTDELETE**
11-03-2001, 04:41 AM
yes the bastard engine has no aftermarket head gasket that i know of..which is why i went the SR route...im sure that guy who is pulling 10s off of his KA has a headgasket.. probably engine specific modified... but who knows... i know there are a few gasket manufacturers who will make a one off piece for you...but you are looking at a 600 dollar head gasket..but you can make it as thick or thin as you want....i say go for a 3mm HG and slap a hairdryer to the ex side of the engine...and blast hondas all day long! ehehhee

**DONOTDELETE**
11-03-2001, 06:28 PM
Thanks MAV1178 ( ALEX ) for that clarification to the young and Innocent http://www.freshalloy.com/ http://www.freshalloy.com/
Alias Spec240sx...

primeral
11-04-2001, 01:12 AM
<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by Nox240:
...im sure that guy who is pulling 10s off of his KA has a headgasket.. probably engine specific modified... but who knows...<HR></BLOCKQUOTE>

I believe Duy's KA turbo was using a stock head gasket. Nissan stock headgaskets are good for up to at least 20psi. You shouldn't use an aftermarket headgasket as a band-aid for bad engine management, as it's usually detonation that kills headgaskets and not overboosting (nevermind about the dude and his friend who killed the motor by not hooking up the wastegate's vacuum lines... dorks)

As for altering compression ratio by drastically changing the thickness of the head gasket, it's a bad idea. You are upsetting the "squish volume" around the rim of the chamber. The combustion chamber is designed so that the charge is pushed inwards as the piston approaches top dead center. A thicker or thinner head gasket may upset the squish volume and you will lose one of the best deterrants of detonation.

<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by 240hp:

never mind about the thinner gasket unless you get a good solid gasket like copper or maybe some of those performance fel pro.<HR></BLOCKQUOTE>

Use of copper headgaskets isn't recommended on street-driven vehicles. Best advice for KA modifiers would be to either get an aftermarket company to make a multi-layer metal gasket, or machine block and head perfectly flat and use a stock gasket.

- Al -

[ 11-04-2001: Message edited by: primeral ]

ADAM HUTCHINSON
11-05-2001, 05:54 AM
i agree...there is a certain falicy with the %loss thru the drivetrain...if you calculated this loss in horsepower and converted that horsepower into WATTS you would have enough heat generated to melt the transmission http://www.freshalloy.com/

so take those %loss figures with a grain of salt http://www.freshalloy.com/

**DONOTDELETE**
11-05-2001, 09:09 AM
<BLOCKQUOTE><font size="1" face="Verdana, Arial[/img]quote:</font><HR>Originally posted by ADAM HUTCHINSON:
i agree...there is a certain falicy with the %loss thru the drivetrain...if you calculated this loss in horsepower and converted that horsepower into WATTS you would have enough heat generated to melt the transmission http://www.freshalloy.com/

so take those %loss figures with a grain of salt http://www.freshalloy.com/<HR></BLOCKQUOTE>
That would be correct, yet very hard to figure without knowledge of the actual heat/wieght/gear play/viscosity, etc...
And as the vehicle goes into motion, it tendancy is to STAY in motion, so loss would be less, Until the HP met with resistance of air and the Trans slip, etc. etc. etc.
So MUCH easier to shoot a 12% lose is closer to overall average.

http://www.freshalloy.com/

ADAM HUTCHINSON
11-05-2001, 08:28 PM
or we can just accept the dyno results at the wheels..and say..who cares about the power rating at the motor since it is not really important...

cause the 10-15% loss like above is out of wack..... if you calculate the hp then convert it to watts...the tranny just could not dissipate that kind of heat....

1hp=746watts of power...

so if we had a 500hp engine rated engine...that loses 15% of its power thru transmission..thats 75hp.....thats 55950 watts of energy to dissipate into the tranny..think about having a 55950watt heater in your tranny....how could it dissipate that kind of heat? i would think most of this energy is used to get the rotational mass of the tranny going..no ? and that would make it a non linear loss..so a linear % could not really be applied? anyone with better math skills have a take on this?