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K24/K20 street build, piston question.

32K views 39 replies 11 participants last post by  Allmotorftw 
#1 ·
Frogive me for this long post lol but I got some questions on pistons. I'm building a frank motor for a DD and was orginally going to use 87.25mm 09 TSX pistons (11.1cr). I'm limited to around 33-35 VTC with the OEM pistons. Lately I've been thinking about changing the pistons because I want to have pistons with deeper valve reliefs/compression. 89/91 octane unfortunately is what I have to work with.

Here is what my set-up consist of:

K24A1 block 87.25mm 09 TSX pistons (11.1cr) (if I decide to use these pistons)
Manley H-beam rods
OEM bearings, stock crank
4piston PRO 156 head, stock size valves, ferrea dish valves
RRC w/ 74mm HR TB (thinking of getting Stefan @ ASP to port my RRC, 400cfm)
RDX 410cc injectors
Drag Cartel 2.2 cams
ASP header, 3in exhaust

I know the OEM TSX pistons will hold me back but this is a true DD car, stop and go traffic etc. Reliabilty > a few more HP. Then again I want to utilize my set-up so I was thinking of switching to these pistons:

87.5mm Wiseco 11.1cr (2618 alloy)
87.5mm Arias 12.1cr (dk the alloy, waiting for them to email me back)
87.5mm CP 11.5cr.

I know the cams will reduce the compression as well as the cylinder head so I was thinking that I could utilize higher compression pistons because of this. The clyinder head will reduce compression because most pistons are made for heads with 50cc and they are really 52-53cc. I talked to Luke awhile back about this but he is hard to get in contact with.

I'm scared to run 2618 alloy pistons on the street in a DD car but I've been told it's easily do-able and longetivity isn't a issue once clearances are in check. Some engine builders have told me to run .0025 with the wiseco's and then some say to run .0030-.0035.

Looking for some experienced opinions/dicussion. I'm probably over-thinking this :facepalm:
 
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#4 · (Edited)
The highest I want to go is 12.1cr, Mahle unfortunately doesnt offer that. This will always be an all motor engine so no boost. I'v heard from experienced engine builers that the 2618 wiseco pistons can last a very long time in a DD car, once well maintained. It's just the piston slap I'm worried about.


Isn't the 2.2 cams only good for 37° advance anyway?
Jeremy said I would have max VTC of 42 degrees with the wiseco pistons. If they're going to make power up to there is another question.

I'm just stuck on what to do, hence why asking for experienced opinions.
 
#5 ·
wiseco's piston is great, i understand you're worried about piston slap that's why i threw you mahle's name.

I don't think many people mention having piston slap problems with the wiseco's. check into what the piston to wall clearance is on them at room temp and operating temp. Out of your choices i'd pick wiseco fyi.
 
#8 ·
piston slap on the wiseco's is pretty low but its still there on cold start.
those are the pistons ill be using on my 2.2 build :) very low expansion.
The 12.5:1cr Mahle's? If only mahle made a 87.5MM 11.5cr piston.

Maybe I'll just get the wiseco's afterall. The piston slap and cylinder wear it what I'm most worried about. As you can see I'm very anal about stuff lol

Any thoughts on the 4p PRO 156 w/ 11.1cr or on the rest of the set-up? I'd love to use higher compression but the gas just doesnt permit it :deadhorse: I'd think with the longer stroke of the K24, this shouldnt be overkill at all.

Here's a link to it:
4 Piston Racing:: Ported Cylinder Heads
 
#11 ·
Depending on your budget and your time frame you could look into getting either a custom wiseco or supertech (mahle IIRC) piston, then you could pick your desired compression ratio and needed valve relief.

I would also recommend the DC 3.2 cams if you are going that route, when I talked to Jeremy he said the 2.2 is more of a k20 cam.

I am doing a very similiar build to yours and am going with custom wiseco pistons with 11.7:1 cr with enough valve relief for the DC 4 cams.
 
#12 ·
Custom pistons will prob be the route I go. How long did wiseco say it would take for the pistons to be finished? Mind if I ask how much for them?

I already got the 2.2 cams so I'm sticking with them.

Whats the rest of your set-up? Bore? stock stroke? ported head also?
 
#15 ·
I just received my spare Z3 head last week, so it hasnt been ported yet but talking with 4piston it sounds like they can get 350 cfm or so out of it. 260-290 cfm is typical of a stock head IIRC. It just depends how far you want to go with it.

I am picking up a ported RBC IM from a buddy thats going with a s/c. The only thing extra i will do is open the inlet up to 70mm to match the outlet of the j37.

As far as valvetrain goes im gonna use supertechs stuff :shrug:

What is your end goal power wise?
 
#17 ·
I'm hoping for around 270whp or so BUT I dont have a dyno in my area so I will never truly know:facepalm:. What about you?

After doing some research, I'm just thinking of leaving my RRC stock, just opening the inlet to fit a 74mm HR TB and port matching it to the head. I keep reminding myself this is just a street DD motor so I dont need to overdue it lol this should be enough fun for a while.
 
#23 · (Edited)
What would I benefit more from: higher compression and less ignition timing or lower compression and more ignition timing?

I'm thinking of just sticking with the 09 TSX pistons and use supertech flat face valves to help retain the compression around 11.1.

Incase I get bad gas at the pump, it would be safer with the lower comp.
 
#24 ·
If you stick to Big name gas like Chevron you really shouldn't have a problem with bad gas, they aren't like those fly by night cash only has stations. I'm running 12.5:1 compression on 91 pump from Chevron.

Those flat faces really won't do much for you at the end of the day, the money is better spent else where.
 
#27 · (Edited)
I'm waiting to get the head back from 4 piston then I'll get it CC'd. After that I'll decide what pistons to go with, I'll keep you guys updated.

Def not 12.5cr though, dont trust the gas around my area.

I live in the Cayman Islands, it's always hot here. Temps rarely fall below 70's or 80's.
 
#30 ·
Still deciding on the TSX pistons or the wiseco's. Will the deeper valve reliefs really benefit me even though I'm staying with the same compression? From what I've gathered, the cams stop making power past 37 or 38 VTC so if I'm limited to 33* VTC with the stock pistons but can run 37* VTC with the wiseco's, how much of a power difference is that?

Never thought a decision would be so hard :deadhorse:
 
#31 ·
Mahle does have 12:1 pistons for k24, they have 4cc domes.

I havent done much with the drag cartel 2.2's but I would say you'd be giving up significant power in the midrange by missing out on that much cam angle.

If you need more info on the Mahle pistons just lmk
 
#34 ·
Any proof of this? With a K24, I dont think midrange would be a problem with the amount of torque they have correct?

Here's a dumb question:wigglesmiley: Say if I get a bad tank of gas, say 89 octane or something and I have the wiseco pistons, how would this affect it? Even if it's only 11.1cr.
 
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