Plate Engine Vavle Spring Testing

Big Chris

Member
Some of you may remember a post from back in early July by Mr Angry titled "Guess how much HP gain w illegal springs"

In that thread there was a side conversation regarding not using high tension springs in the plate engines and phenomenon I thought I identified. The conversation continued regarding beat frequency oscillation between myself and astglenn.

Whelp for all you doubters out there, I think I've dialed it in.

This is a AKRA legal clone with a certain spring, a certain valve, and certain amount shimming. (and yes Al, jetted just right) That info I'll keep to myself, as it's taken tons of work to get this right. (including building a spring "dyno") I will hint to this, it will easily pass spring tech.

Peak HP moves to 5500 rpm in a purple plate engine, and 5250 in a green plate. YES it's repeatable, and with the amount of pulls its taken to dial it in, I'm very confident it's stable for the long run as well. Although it is hard on the valves.

Geared correctly, this one is hard to out-horsepower on the track.

These screen shots are a purple plate clone.

Peak%20HP%20testing%20082215%20%2001_zpswhvpbgxn.jpg


Peak%20HP%20testing%20082215_zpsnvx8kce7.jpg
 
I'm wondering why my chart comes up with different HP numbers.
RPM Torque HP
3000 10.44 6.45
((A8*B8)/5252.1)*$A$5
A8 = RPM
B8 = Torque
A5 = 1.082
$A$5 = Correction Factor
I'm wondering; why would you have corrected torque and corrected horsepower? Maybe that's why I come up with different numbers?

I want my dyno program to be as accurate as possible, any suggestions?
 
The software compensates to meet variables in Barometric pressure, air Temperature and humidity. Mine corrects all readings to 29.92 bp @ 60 degrees with dry air. Thats why you can dyno the same engine on a 90 degree day with 48% humidity and 29.18 bp and again on a 65 degree day with 80% humidity and 29.0 bp and get the same results. The correction factor is how much the results were adjusted by the computer.
 
The software compensates to meet variables in Barometric pressure, air Temperature and humidity. Mine corrects all readings to 29.92 bp @ 60 degrees with dry air. Thats why you can dyno the same engine on a 90 degree day with 48% humidity and 29.18 bp and again on a 65 degree day with 80% humidity and 29.0 bp and get the same results. The correction factor is how much the results were adjusted by the computer.

^^Exactly.. without weather correction..its just a guess..IMO
 
Nice pickup in the 5500 and up range. On run #17 I see you lost a touch on the bottom and picked up on the top end nicely. That's what I saw when I was playing with them over lbs springs but I believe your going the other way. Can you give the matrix for the test. Spring lbs changes only using shims with same valve or different springs etc etc
 
.
I'll do a comparitive graph later comparing this setup with a set of new "green stripes".
As for what exactly I've got going on here, man I bet I have close to 60 hrs spent on just this, not sure I want to just give that up.
 
Yepper, I dialed this in a long time ago and have been using it successfully for 3 years now. Except with continued work, and the cam selection we have now, the HP drop off seen in the orginal post at around 5800 ish rpm has moved up to well past 6300 rpm for a purple plate engine (big pipe)

See 2nd post in this thread for dyno screen shot, note that I'm within .12 HP of peak power from 4500rpm all the way up to 6000 rpm.

https://karting.4cycle.com/showthread.php?93599-Purple-Plate-Clone-Gearing&p=695895#post695895

As for exactly how I do this, all I'll say is the devil is in the details.
 
I've played with this a bit in the last few months with green and purple plates but we're using a small pipe, I've seen gains but I haven't got to 6300 yet, I wonder how much of that is in the pipe?
 
All of it, by design the little pipe limits power in the upper rpms.
Look at the recent loose muffler thread for dyno data regarding the little pipe. What you see referenced above is the big pipe.
 
Chris,

I'm curious if you've done much testing with the weenie pipes on Purple plate engines as mandated by so many tracks now? We're stuck with it here and currently can't seem to get much above 5800rpm with our current setup. I know the small pipe really restricts top end I'm sure.
 
the way I see the graph its down one full hp at 5800rpm from the hp at 5400 rpm.
why would you want too turn it that tight?
 
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