Please explain this!!!

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Please explain this!!!

Postby snd93 » Fri Oct 06, 2017 8:06 am

Brand new non overdrive shockwave. Orange spring front and rear, driven one hole right of nuetral. 12 tooth front, 85 rear. How did it go into overdrive? The gearing is set correctly in the mychron 4.

I'm also not happy where the clutch engages at 6,300 rpm. I would like to see it engage quicker. A purple spring should help that, correct?

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Re: Please explain this!!!

Postby drags3078 » Fri Oct 06, 2017 12:41 pm

Looks like a nice gragh to me .. Did you set tire circumference as far as the overdrive ??
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Re: Please explain this!!!

Postby snd93 » Fri Oct 06, 2017 1:01 pm

drags3078 wrote:Looks like a nice gragh to me .. Did you set tire circumference as far as the overdrive ??


Yes, tire circumference is set at 56.5" in the mychron. You can stack the graphs on top of each other and they all match. Only a very, and I mean VERY slight change in the first 30'. The rest of the run the graph lines are stacked on top of each other with no deviation.

But also, the car ran a 10.39, 10.42, 10.45 and then a 10.54. I don't treat the tires during the week or between rounds and track conditions stayed the same all night.

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Re: Please explain this!!!

Postby RNorton » Sat Oct 07, 2017 12:42 am

Can you post incremental times and MPH for those ET?

Did you track weather?
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Re: Please explain this!!!

Postby WOLFRACING » Sat Oct 07, 2017 8:29 am

I'm kinda curious about the replies to this question. Why would the tire diameter or the gear ratio affect the jackshaft speed reading? Or the weather?
I think the OP wants to know how the jackshaft can be spinning faster than the engine without overdrive. I think the answer is that you can actually pull a little od on non od clutches. Particularly on applications where you run out of gear pretty early in the run like you are. I didn't see any details, but is this a raptor engine?
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Re: Please explain this!!!

Postby snd93 » Sat Oct 07, 2017 9:08 am

WOLFRACING wrote:I'm kinda curious about the replies to this question. Why would the tire diameter or the gear ratio affect the jackshaft speed reading? Or the weather?
I think the OP wants to know how the jackshaft can be spinning faster than the engine without overdrive. I think the answer is that you can actually pull a little od on non od clutches. Particularly on applications where you run out of gear pretty early in the run like you are. I didn't see any details, but is this a raptor engine?


THIS It baffles me.

This is Raptor. Hot stock cam (2.90 lift) with some porting, .20 over bore with a 4.75 arc rod.

RNorton wrote:Can you post incremental times and MPH for those ET?

Did you track weather?


I do track weather but the only thing that I have found plays a huge part is the wind. I don't know enough about these little engines to know what effects what. Like what do temp drop do to the ET or lower humidity, etc.

Here are the incremental shots.

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Re: Please explain this!!!

Postby jtracr » Sat Oct 07, 2017 9:12 am

Gear ratio plays a big factor into your answer. A lower gear (7.09:1) will use a lot more of the clutch than if you had lets say a 5:1 or 4:1 gear. This is the same reason when we run a 4.5:1 gear WITH an over-drive we don't see any over drive, usually about 92% at the finish. Way back when we ran 12.90 we ran a 22/66 gearing. (3:1) At the finish we would see 6450 engine RPM and 2900 Jackshaft, those were really odd looking graphs!
So yes you can get a little bit of OD out of a non-OD clutch.
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Re: Please explain this!!!

Postby snd93 » Sun Oct 08, 2017 11:30 am

The clutch is engaging at 6,300 RPMs. Would a standard purple spring make it engage quicker?
I can’t raise the staging RPMs any higher than 4,000. The engine starts to hunt.
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Re: Please explain this!!!

Postby jtracr » Sun Oct 08, 2017 12:11 pm

Not sure on shockwave stuff but Terminator purple is higher stall than orange. What are you trying to fix? Is it a reaction time issue? A softer spring will more than likely loose et, thus slower. Let's say you get the car to move at 5500. If you were to Dyno your engine compare how much HP you make at 5500 compared to 6300, most engines make considerable more HP at 6300 than 5500.
I would check belt air gap and tension too. You might have the correct spring and just be off on those. Good luck.
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Re: Please explain this!!!

Postby Pool Man » Thu Oct 12, 2017 10:00 am

A loose belt can result in getting overdrive.
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Re: Please explain this!!!

Postby snd93 » Thu Oct 12, 2017 10:02 am

Belt is tight!!

I put a purple spring in it last night to help with the high RPM at engagement. If the rain holds off, we're going to GALOT tonight for TNT. I''ll update with the results.
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