Question about boring/stroking - Toyota Nation Forum : Toyota Car and Truck Forums

brink · 12-02-2003, 01:26 AM

So I was thinking, my 2.2 liter is supposedly 135hp at the crank. That's about 61.4 horsies per liter. With straight math, boring out/stroking it to 2.4l would give me an additional two tenths of a liter, which would be an extra 24.5hp.

Thing is, that doesn't sound like that significant a gain for the amount of effort involved. I mean, sure you've got another 25, but that's crank horses, not wheel horses. You're going to loose 20-40% of that through the drivetrain yielding an improvement of 16. So, is the power/displacement linear or exponential? I guess I'm just wondering why you'd do that, unless it was part of the whole-car setup.

97KaMuRi · 12-02-2003, 04:54 AM

i have seen a 2.5 stroker kit for the 5s-fe somewhere. but i cant remember the site but i know it is out there though.

Nick · 12-02-2003, 05:35 AM

well the boring out gives you a higher compression ratio, more area in the cylinder, same head, so i'd say it goes up exponentially

and its 640 am, haven't gone to bed so i'm not gonna think about the stroker part, i can't remember if it makes the travel shorter or longer

NOTSOFAST · 12-02-2003, 06:23 AM

It makes it longer !! So u get more displacement. And I think It would reduce the compression ratio, normally !unless make longer strokes without boring, than it would increase it !!!

Nick · 12-02-2003, 01:19 PM

longer stroke would up the compression ratio, think about it

volume at bdc/ volume at tdc if the bdc is lower, the top will still be the same,

88 LE · 12-02-2003, 03:20 PM

Quote:

Originally posted by Oldman
well the boring out gives you a higher compression ratio

Boring increases displacement not compression ratio.

Nick · 12-02-2003, 04:00 PM

oh right at tdc you'd still have a bit of an extra diameter there

arcasmachineracing · 12-03-2003, 01:08 PM

yup oldman... 'stroking' is all you like to do... ok nuff of that shit... stroking can be achived via incresed piston length or or rod length. As if you guys didn't already know that.

88 LE · 12-03-2003, 05:36 PM

Quote:

Originally posted by arcasmachineracing
stroking can be achived via incresed piston length or or rod length. As if you guys didn't already know that.

Stroke has to do with the crank not the length of the piston or rod.

If you increase the length of the piston or rod all your doing is moving the piston up or down within the block. The stroke stays the same.

The only way to increase stroke is to move the position of the rod journals on the crank.

arcasmachineracing · 12-03-2003, 06:49 PM

Quote:

Originally posted by 88 LE
Stroke has to do with the crank not the length of the piston or rod.

If you increase the length of the piston or rod all your doing is moving the piston up or down within the block. The stroke stays the same.

The only way to increase stroke is to move the position of the rod journals on the crank.

:o Damn High School Auto Class!

Muh bad. Thanks for correcting me 88LE.

alltrac165 · 12-05-2003, 01:28 AM

Actually, your math is off. You would only see about 12.3 hp increase. If you've got 61.4 hp per liter then 1/10th would be 6.14 and 2/10ths would be 12.28. Makes it even less cost effective, eh?

The increase in power is roughly proportional to the increase of displacement. As you go up in size, you'd need to increase the breathing ability of the intake, exhaust, etc. to keep up or you would see diminishing returns. As far as why, it's part of the package. All by itself it's hard to justify the cost, but if you increase the displacement by say 10%, then you have the potential to increase the power by roughly the same even after you factor in all other mods. For instance, if you are pumping out 400 hp via a nice turbo set up, then that extra 10% means 40 hp.

Any increase in displacement that does not increase volume in either the piston top or the combustion chamber will increase the compression ratio.

A simple increase of bore will yield more of what you have across the board in very general terms. With no other changes to the engine, you should have an increase in hp and torque everywhere.

A simple increase of stroke should yield a similar increase but with a greater emphasis on torque than bore alone. Since you have moved the leverage point of the piston rod further from the center of the crank, it now enjoys better leverage on the crank and thus is able to generate more torque. This is why truck engines generally use a smaller bore/longer stroke ratio than car engines. It also increases piston speed at any given rpm over it's shorter stroke counterpart which leads to a lower safe rpm limit as far as the rotating assembly is concerned.

The nice thing is it's a power increase with no real downsides and it allows for larger improvements when coupled with other mods.

Wraith · 12-09-2003, 03:29 PM

the biggest stroke you can go on a 5s-fe block is about 97mm and the bore would be 92 to 93mm ... But this requires resleeving