06-12-2011, 08:17 PM #1
- Join Date
- Jul 2010
- Hueneme Beach Ca.
This doesn't make sense. Any guesses?
My FZ ran exactly 8150 RPM last week. It felt like it was being held back somehow.
I was running a 13-24 prop and stock nozzle.
I switched to a 13-23 an adjustable nozzle (82MM ring installed) and the R&D anti cav cone and it ran exactly 8150 RPM again but was a couple of MPH slower.
The tach is rock steady at 8150 ( I may see a flash of 8160 periodically).
If I pin it out of the hole and let it cavitate and hit the limiter (I know, I know) guess what? 8150 again.
It really just seems like it's limited at 8150.
I thought the R2 program had a limit of 8500 or something, I've forgotten exactly what.
While I'm certainly not an expert on this particular platform, I'm pretty savvy when it comes to superchargers and high horsepower engines in general.
I have designed superchargers for and built some of the fastest Corvettes in the country, if not the world.
I do all the PCM programming for the Corvettes and have a pretty good idea of what's going on in the fuel and spark curves and how it affects power output. (not this particular computer, however)
This one just seems like it has hit a wall and no matter what I do, It really doesn't make much difference.
I ran a B1 wheel last year and although it does accellerate harder with the E1, It still feels like it hits the limiter at just over 80.
If I get in a little chop and the prop unhooks, it seems like the added RPM would give you a surge forward when it gained traction again. It really doesn't seem to do that.
Any ideas as to what I'm missing?
With the mods I have listed, should I have the R3 program, anyway?
I'd like to avoid going with a Motec because I'm just a recreational rider and really only go out 6 or 7 times a year. But if a Motec is what I need to make me happy, that's what I'll do.
As much as I would like to be able to log it, see exactly what's going on and tweak it regularly, I really just want it to do an honest 83-84, ride it and not have to mess with it.
I think I have more hours modifying it that I do actually riding it.
Actually, if I think about it, that's the same story with both my Z06 and my Trailblazer. I drive them both with computers hooked up, logging and tuning. I'd rather not have to do that with the Yamaha.
Seriously, any help would be appreciated.
06-12-2011, 08:30 PM #2
- Join Date
- May 2010
06-12-2011, 08:41 PM #3
what kind of tach are you using? and are you monitering your air fuel ratio's?
06-12-2011, 08:59 PM #4
Your a tuner. Stop guessing with reflashes.
06-12-2011, 09:09 PM #5
:R2 is limited at 8750, were you wearing your bi-focal sunglasses? Maybe that "1" was a "7"?
Seriously, if you weren't seeing 8150 on cavitation rev, I'd guess your prop and nozzle swap cancelled each other out. Some of the earlier reflashes had different setting values than the newer ones do. I ran into this with my very early R2 flash which had different fuel mapping than the newer R2 flashes do. I switched to the R3 flash to do away with the powershot, although others with nearly my identical setup are able to manage on a R2 without a powershot. If you've had your R2 since last spring or summer, Glen at R&D should be able to tell you if the rev limit has changed.
06-12-2011, 09:13 PM #6
A couple things I'd look at before continuing to experiment with pitch & nozzle size:
engine tune...IMO, you should be turning more rpm with those pitches with an E1. If you're testing in salt, that explains part of it but it still seems low to me. I've never tested with an E1, so maybe someone who has a similar setup as you can chime in.
true prop pitch...you need to check them on a gauge. Many props I've bought have been as much as +/- 1 degree off out of the box
This thread has some really good info that will help you understand the effect of changing thrust & velocity using different nozzle sizes:
06-12-2011, 09:32 PM #7
Ive always run a 13/25 with stock nozzles had no problem doing 86.5mph @ 8700rpm on stock motor E1 all day long.
06-13-2011, 12:45 AM #8
You went down in prop pitch, which adds RPM, but then you choked down the nozzle at the same time, which made you lose what you would have gained, and made yourself lose even more RPM by adding the anti-cav cone. This is why Mark was saying it's better to test one thing at a time when playing around with pump and nozzle combinations.
Go back to the stock nozzle, and stock cone, and leave the prop in there. Wouldn't be a bad idea to measure the prop because they absolutely can be out a degree or even more right out of the box.
I also agree that you should be building more RPM with your E1 wheel and the reflash you are running. So there could be something else going on. Would help to know your AFR and boost numbers. When dialing in one of these skis, you will start to lose RPM if you go too lean or too rich.
06-13-2011, 09:43 PM #9
- Join Date
- Jul 2010
- Hueneme Beach Ca.
I don't trust myself to get a tune for a supercharged car right on the money without being able to datalog it..
I have read that everyone seems to be very happy with these R&D flashes so I figured I'd go that way. I did run it with a wideband before I ran it wide open just to be safe.
I have 81, 82, 83 and 84 MM rings to play with.
Do you really think that less than .5 MM on the ring and the addition of the R&D cone could completely nullify the prop change, as far as RPM is concerned? The fact that it ended up at EXACTLY the same RPM but lost almost 3 MPH is very suspicious.
Does R&D (or anyone for that matter) tune skis? I'm to the point where I would like to take it to a shop and say "here, make it work"
I know it's not the same as my shop where I have a dyno and can roll the car on it and tune it. I'm not sure how they would even go about it. I know that they have "test tanks" but you can't replicate a top speed run in one of those. At least it doesn't seem like that would work to me.
I suppose they "may" be able to dial in the AFR but I'm assuming that getting the RPM straightened out with prop size etc. is strictly a ride it and see deal?
06-13-2011, 09:48 PM #10
Turning a LS motor with the PCM system is alot different to just buying a reflash off the shelf. At least you can see the mapping on the PCM system.
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