timing vs power

[longsled]

can we feel a noticeable power increase by the timing modification? on boost, my timing is moved 2.5d from the stock timing.

on full-c12 fuel @ 15 psi low comp. piston, does I will have a noticeable power increase if I'm putting the timing back to 0 (stock timing)

thanks.

 

[DC5]

Probably not but it depends on what the stock timing is. I am assuming that you are talking about your 1200 ski-doo. If the stock timing is very aggressive you may make more power with the 2.5degrees pulled. Someone with more experience with the 1200's may be able to chime in.

 

[mbarryracing]

Longsled,
The 1200 has a pretty good volumetric efficient cylinder head so it's timing at higher speeds isn't very advanced to begin, just with like you stated, 0 degrees...

Did you retard 2.5d or advance 2.5d from stock 0 deg?

The straight C12 fuel you are using burns slower then pump gas so that will influence things as well.

One way you could tell is take your RB3 and crank the timing back (retard) from stock and see if your clutch shift RPM increases, like over rev from your existing clutch setup, telling you if you are making more power...

My limited experience with on Yamahas is that I haven't seen a significant gain in peak power from changing from stock (if any) but will gain throttle response in lower RPM's.
Maybe someone like Hurricane Dave can add to my statement ?

Again that doesn't really mean you'll experience this same on the 1200 Rotax.

 

[Turk]

I talked to Dave on running a different ecu on my turbo RX-1 that retards timing on the big end. He said on the dyno & in the field they lost a lot of hp by retarding timing on a rx-1.

 

[DC5]

I talked to Dave on running a different ecu on my turbo RX-1 that retards timing on the big end. He said on the dyno & in the field they lost a lot of hp by retarding timing on a rx-1.

I think the Apex's gain a little power from retarding timing about 2 degrees.

 

[longsled]

on boost I'm at +2.5d from stock.

 

[mbarryracing]

on boost I'm at +2.5d from stock.

That might be just right for your VP C12, might not be the same for other fuel though.

Have you tried the stock timing?

 

[longsled]

it was last year with fpp kit, not timing alteration.

the pre-program from powderlite came like that, -2.5 under vacuum and + 2.5 on boost.

I'm talking for racing application.

just want to know if theoretically 2.5d can make a difference on drag racing.

 

[HURRICANE]

Nick is right.The Apex will make more power with less timing on the big end.The RX1 will not.Yamaha already has the RX1 in the sweet spot but if the timing is advanced on the RX1,it will not loose power but will gain 20flbs on the bottom.The stock timing is best also on the 1200 doo engine.We lost 10hp by pulling timing on the dyno.
This is all on moderate boosted engines on pump gas.You will generally add timing if switching to race gas with a high specific gravity.

 

[mbarryracing]

Longsled,

Speaking theoretically, timing is retarded from stock settings on engines with cylinder heads with less then efficient combustion chambers after being boosted or compression is increased which creates a more efficient (or faster) combustion in those engines. These engines would typically have +5 to +10 deg (or more) advance timing at high RPM's in stock form in order to compensate.

These sled engines have way more efficient cylinder heads that burn quicker stock (reason why the Yamaha's run 11.5K RPM) and require less timing advance at the higher RPM's, (you know that by the 0 deg timing on the 1200).
So theoretically their high RPM combustion doesn't get much more efficient (or faster) under moderate boost (say under 25 lbs) so retarding the timing doesn't gain anything but higher exhaust temperatures. Advancing the timing will lower exhaust temps, that has to effect boost somewhat?

I have yet to see a dyno comparison showing a considerable peak HP difference that you'd actually see at the boost levels you and I are running to make it worth screwing with the timing. Now maybe at full race levels like the outlaws are running (30 lbs+)... so not saying this is hard fact, others have more experience here.

Again, this I only am speaking about peak RPM & HP and not throttle response at lower RPM's, and fuel dictates alot of the results. One fuel brand will burn slower then the same octane of another brand and therefore could respond different to change in timing.
Dave is right on, usually pump fuel burns the quickest so uses less timing, race fuel burns slower.
All I can suggest is try dropping your current 2.5+ back to stock 0 deg and make a pass.

 

[longsled]

Longsled,


All I can suggest is try dropping your current 2.5+ back to stock 0 deg and make a pass.

will try, it was working without any timing alteration last year, I just wondered wich one is better.

pretty hard to look at rpm with that dynamite sled on a pull and finding wich one is better....

 

[mbarryracing]

With the racing you are doing, might be worth looking at the Mountain Performance Pro-Logger so you can record and playback RPM, Boost, AFR and also a boost controller all in one for almost same $$$ that I have wrapped up in separate gauges and boost controller.

 

[longsled]

I'm wondering if rb-3 can log the RPM end playback some pass. I had looking at it but I didn't found anything about that in the software.

My AEMa/f have a analog output and it can be connected to rb3,..

pro-logger will be probably added next year with a electric boost regulator, but for this year, it's enough...... just replaced track, cheezels and drive shaft this week, and it's running only since 10 days. need some spare $ for the rest of the winter, just in case..............

 

[longsled]

I'm wondering if rb-3 can log the RPM end playback some pass. I had looking at it but I didn't found anything about that in the software.

My AEMa/f have a analog output and it can be connected to rb3,..

pro-logger will be probably added next year with a electric boost regulator, but for this year, it's enough...... just replaced track, cheezels and drive shaft this week, and it's running only since 10 days. need some spare $ for the rest of the winter, just in case..............

 

[longsled]

I'm wondering if rb-3 can log the RPM end playback some pass. I had looking at it but I didn't found anything about that in the software.

My AEMa/f have a analog output and it can be connected to rb3,..

pro-logger will be probably added next year with a electric boost regulator, but for this year, it's enough...... just replaced track, cheezels and drive shaft this week, and it's running only since 10 days. need some spare $ for the rest of the winter, just in case..............