07-04-2008, 07:52 PM #1
- Join Date
- May 2008
results on mods, info and question?
so i finally got all my mods in last week. took it out and it felt very fast but had nothing to compare it to. still had the stock prop in too. the acceleration was insane but was hitting rev limiter. so for this weekend i installed a solas 15/20r with an 83mm ring. took it out yesterday and the dreamometer would not go past 69 mph although this was at 7400 rpm and a little over half throttle. At full throttle rpm went to 7900-7940 but speedo still only read 69 mph. maybe thats the most it reads. so i was a little bummed out because i didnt know how fast i was going and stopped by Best Buy and got a gps.
so went out today and ripped a 75.8 mph on the gps @ 7900-7940 rpm. my stock s/c was getting 8.1-8.3 psi which is insane. my a/f ratio at wot was 13.2-13.4. a little rich i thought. conditions were 84 outside temp and 74 water temp. 1 click above neutral on vts. 1 bar over half tank and i'm about 175 lbs. also i have the 83mm ring in. my questions are if i went to a smaller ring i gain speed but lose acceleration and rpms. also shoud i chase the 160-200 rpms tweaking the prop. pros vs cons? lastly i want to say thanks to this entire forum couldnt have done it without you guys. i need lots of feed back to. thanks again
Last edited by vduzin12; 07-04-2008 at 07:56 PM.
07-05-2008, 07:49 AM #2
I would say leave it where it is.
The wish o meter will only read up to 69 - I guess they felt that was a nice number to stop at. You will find it is off by about 5+ MPH, mine showed 69 quick and kept accelerating but on the GPS showed only 65 peak at that time.
If you make the prop taller you will lose RPM. With the 83mm ring you are turning the most RPM. Putting smaller nozzle ring in will choke it out causing less RPM and since you are at 7900-7940 you donít want to be less since you want it to be around 8100. Not sure what your other mods are, but if you make another small upgrade you will be right where you want to be.
07-05-2008, 11:34 AM #3
13.2 - 13.4 is a little lean, not a little rich. For engine safety and longevity, you want to be about 11.8 - 12.2:1 at WOT. You can be lean up until the motor gets to 0 vacuum/boost (5000 RPM or so). After that, you need to be on the rich side. Heck, you could even be 15:1 at idle and up to 3000 rpm or so as the motor is not under any load and it would have no ill effects. Under boost, you need to be rich to stave off detonation. Just one run with crappy gas under full boost and a lean-out condition will chew away at the head gasket and piston surface.
I would pitch the prop to get your last 200 rpms back and use your nozzle to adjust for temperature throughout the season. If you pitch your prop to get close to max rpm during the heat, then you can always step down the nozzles as is cools off outside and gain top end.
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