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Discussion Starter · #1 ·
Let's talk piston speeds and the srt-4 engine.
Anyone got piston speeds by RPM or a calculator?
Anyone stroke the motor yet?
What piston speeds can the stock rods handle?
 

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Our piston speeds are up there and I'm too tired for math right now. :zzzz: If anything I would destroke this motor a tad and try to get a better rod ratio going.

Stroke(in inches) x RPM divided 6 will give you the piston speed (in feet per minute).
 

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I dont know what the big deal is about piston speed... I`ve built engines w/ 4.750 stroke and spinning them 8000rpm!! :wah?!: That makes the piston speed for the SRT look like nothing..

[email protected] 8000rpm = 6333fpm!!! :wah?!: :wah?!:

So STOP your cryin` about piston speed!!!
 

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Discussion Starter · #10 ·
BRUTE4Z said:
Our piston speeds are up there and I'm too tired for math right now. :zzzz: If anything I would destroke this motor a tad and try to get a better rod ratio going.

Stroke(in inches) x RPM divided 6 will give you the piston speed (in feet per minute).
Thanks for the calulator man. :clap:
 

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Discussion Starter · #11 ·
SY04SRT4 said:
At 6000 RPM it's 3984 FPM. At idle (or around 800 RPM) it's 531.2 FPM. I love HP Books' Auto Math Handbook!
Exellent info man! Thanks :)
 

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Discussion Starter · #12 ·
SRTper4mance said:
I dont know what the big deal is about piston speed... I`ve built engines w/ 4.750 stroke and spinning them 8000rpm!! :wah?!: That makes the piston speed for the SRT look like nothing..

[email protected] 8000rpm = 6333fpm!!! :wah?!: :wah?!:

So STOP your cryin` about piston speed!!!
That's cool but is this motor (that you have not built) able to handle those kinds of speeds? Throwing a rod is not fun.
 

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Discussion Starter · #13 ·
Ok guys let's say you are dead set on stroking the motor what would be the weak points you'd address? what would you need to rev a stroked srt mortor to 8k?
 

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Discussion Starter · #15 ·
shmirgin44 said:
whaddya you doin now Coleman? :lol: Just get S3 and stop breaking ur car! :thumbsup:
Stop breaking my car??? I hear someone is getting an new trans because they can't install and STS :jester:
 

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Piston Speed

Piston speed in general is a relatively obscure issue, and all anyone in this forum has talked about is "Average piston speed". Piston Speed is not linear. Some engines have piston speeds at certain points while travelling down the bore that are astronomical! I have raced NHRA Pro Stock where the piston speeds are high, and have built 814 Cubic Inch IHRA Pro Stock engines with 5.900 stroke Crankshafts, and 8.00" connecting rods turning 8400 RPM through the lights, which is piston speed insanity, and leaves engineers scratching their heads...but pistons hold up fine. The SRT 4 piston is light years away from this type of abuse. The SRT 4 for example has a realtively short connecting rod in relation to the stroke length with about a 1.5 to 1 rod to stroke ratio...this is a fairly decent approach for an engine with a redline which is relatively low, and an induction system which is relatively efficient. The rod to stroke ratio in the 2.4L engine doesn't allow the piston to dwell at TDC for an excessive amount of time, therefore getting the piston "out of the way" more quickly for a better cylinder fill...also the piston dwells at BDC longer for a better fill. This coupled with a good cam selection produces strong smooth flat torque curve which helps in moving the vehicle. This is important during gear changes when the RPM's drop...the engine will tend to come back up through the RPM range more quickly after the gear change.
The bottom line is that piston speed is not even an issue to consider in any buildup an SRT 4 owner might imagine for this 2.4 liter engine. Definitely don't listen to the Honda fanatic and destroke!
I have 2 Custom 4.375" stroke crankshafts on order for a customer of mine with an SRT-4. I will be using a "Chevrolet" billet rod, and a custom Venolia piston. The engines will be 2.8 liter. Also the head will be ported. By the way, I will have a quality CNC version of the SRT 4 head ready after the first of the year, so all us SRT maniacs can flow some air, and make more HP. At the present I am able to get the airflow numbers up an average of 20% (on both intake and exhaust) over the stock heads numbers. After I get the head where I want it, I will digitize the head for reproduction on my 5-Axis CNC machining center. I will be dynoing an SRT 4 this winter when business slows a little. I will send a thread to SRTFORUM with the before and after numbers to the stock SRT 4 with no other mods...then progress from there. If anyone would care to contact me for any reason, please feel free...I also have a complete machining facility devoted to racing engines in the event anyone needs "anything" done to their engine. [email protected] Thanks
 

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Dude TK you rule. I am glad to see more people wanting to make products with "real results" not the bullshit adds that the CAI section has so readily adapted. From what i have read the only real hold back with the SRT motor is the head flow numbers, and it sounds like your doing a great job of fixing that. Keep up the good work man.
 

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Dude, TK Racing you totally rule. I really like what you are doing. You should become a vendor when you finish your products(I don't like to call them vendors, rather suppliers), because you could make some serious horsepower for us.
 
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