Piston Crowns

[contraption22]

The way I understand it, the dome on the OE SRT-4 style piston helps to ward off detonation, but a conventional piston crown would be better for power.

Assuming the same compression ratio, which would you use and why?

I am looking to build a relatively mild 2.4, and budget restictions would likely te me to SMEC electronics.

Thanks,

Mike

[turbovanman²]

I asked this on the SRT forums-

http://www.srtforums.com/forums/f169...i-jump-615987/

[contraption22]

Thanks for the link Simon.

I wasn't brave enough to ask a tech question over there. lol

Still interested in input from the T-M community.

[turbovanman²]

Thanks for the link Simon.

I wasn't brave enough to ask a tech question over there. lol

Still interested in input from the T-M community.

Too funny,

[ShelGame]

I think the 'ski-jump' shape is for tumbling the charge in the chamber for mixing purposes; as a result, you get a slower burning charge (and probably a smaller peak cylinder pressure, but a high average cylinder pressure; and it for sure has an emissions effect, too), which then requires more total timing. I think that's why the SRT4 has so much ignition timing compared to a dish-piston design.

I would think the the ski-slope design would also reduce port flow when the piston is near TDC. Granted, that's low valve opening, but still. I'm not sure how (or even if) that suspicion could be confirmed...

[BadAssPerformance]

I am looking to build a relatively mild 2.4,

For a mild 2.4L on a budget, hard to beat the stock SRT internals if you are using the later block/head anyways...

[turbovanman²]

I would think the the ski-slope design would also reduce port flow when the piston is near TDC. Granted, that's low valve opening, but still. I'm not sure how (or even if) that suspicion could be confirmed...

That was brought up in another thread, I don't think that's a valid claim as bikes use pistons that match the chamber and they make stupid HP per CC.

[contraption22]

For a mild 2.4L on a budget, hard to beat the stock SRT internals if you are using the later block/head anyways...

I'll be using an early motor. It's already been bored .020. Just needs a finish hone to match whatever pistons I end up getting. While the combination will be mild, I definitely want the peace of mind of having forged pistons. I'll probably use Eagle rods as they are good enough for my goals.

[johnl]

Generally speaking, if you can reduce piston/chamber surface area, that's usually a good thing. Less surface area to suck up heat, so more heat/pressure to drive the piston. For that reason, domes and ski jumps and the like are almost never optimal.

[ShelGame]

That was brought up in another thread, I don't think that's a valid claim as bikes use pistons that match the chamber and they make stupid HP per CC.

Yeah, but bikes have stupid high compression, too - like 13:1. The SRT is 8:1. Bikes also don't have to worry about HC emissions so much. Chrysler raised the crown for a different reaon (I beleive for tumble induction), and then dropped the piston down in the hole to get the CR down. Usually, anything done to induce tumble is not good for flow.

[BadAssPerformance]

I'll be using an early motor. It's already been bored .020. Just needs a finish hone to match whatever pistons I end up getting. While the combination will be mild, I definitely want the peace of mind of having forged pistons. I'll probably use Eagle rods as they are good enough for my goals.

I have had good luck with the JE's in my earlier motors... I have a spare set in the old 2.4L that was in it, but IIR they are are .040's. Heer is a pic of one of the originals before living thru 2 oil pump faliures

[contraption22]

I have had good luck with the JE's in my earlier motors... I have a spare set in the old 2.4L that was in it, but IIR they are are .040's. Heer is a pic of one of the originals before living thru 2 oil pump faliures

Yeah, I am definitely going with JE's. I have had good luck with them in the 2.2 8v. But I have the option of the dished or the domed. If money were no object, the dished would be the easy choice. I have the option to use a set of un-used take-out domed JE's or ordering a new set of dished pistons. I guess the dished will be the ones to go with.

Thanks all for your input.

[turbovanman²]

Aren't people making good power with the stock style? If so, I would use them if you have them.

Also, if your not going for all out power, then I think the choice would be to use them, save yourself $500+.

Anyone tried JE's new FSR piston?

http://www.ebay.com/itm/JE-FSR-Forge...item4ab47e05c2

[ohiorob]

I've used JE and Wiseco and liked them both. Wiseco comes with light tension rings and are not file fit but worked great for me. if you are going to really pond on them I would go with the upgread ristpins. for the money Eagle H beam rods are awesome, don't know why some people down grade them. What car is this motor going into and is it going to be at SDAC this year.

[contraption22]

The motor will be going in my Horizon. The goal is to have it be a consistent mid 10 second combination, ideally without the help of nitrous, but it will be on the table if needed. Budget constraints require that I use as many parts that I already have as possible, but if spending a little bit of extra money in the shortblock will help the rest of my combination work, then I'm willing to do it.

Steve M. ported head. Gonna stick with stock 2.0 cams and some good valvesprings. I won't be revving it very high so I should be ok there.
S50/S3
Cast iron exhaust manifold. I have a Mexican manifold, but I may go with a Treadstone if it fits better in an Lbody.
I have a big-plenum manifold that my brother constructed for is 1st gen Neon, but I don't think it will fit an Lbody.
There will need to be some money spent on a good intercooler and a better engine cooling system.
Fuel system will need a complete re-engineering.
Also want spend money on a good trans and converter.

I've also toyed with the idea of having it run in E85. An E85 pump just popped up on the direct route between my house and the track.

I'll probably be at SDAC, but the car will not.

[BadAssPerformance]

GLMFSRT

Still havn't stumbled across that mount...

[contraption22]

GLMFSRT

Still havn't stumbled across that mount...

It would be great if you did!

[BadAssPerformance]

It would be great if you did!

Gremlins I tell ya... I looked in every other place I thought I'd put it the last time we talked. Believe it or not, I got too much stuff! LOL! I'll check again...