rpm limitations

Quote:

Originally posted by GLHNSLHT2 Oh, and the 2.5 has a longer stroke than a 440 Mopar which has a longer stroke than that crappy 454 GM joke. Later

Here's an even better example. GM 396 has 3.76 stroke, Mopar 383 has 3.38. In 69'-both 325 hp versions. MP-425 ft/lbs, GM-410 ft/lbs with MORE cubic inches and longer stroke!

[Aries_Turbo]

yeah the honda is a bit undersquare but not just our bore and stroke are the limiting factor.... everything about a honda motor is built around revving high and making high specific output. the internals are light, the displacement is small, the cam grinds, the heads, the pistons.. you name it.... its built to rev. the 2.2 and the 2.5 just arent that type of motor.... they are stump pullers, fairly large displacement 4 cyls with strong heavier internals and heads set up to make torque, and lots of it. ive had screamers and ive had torquers and ill take my torque.

Brian

[glhsken]

GLHNSLHT2 I'd really like to see a dyno plot of your engine. That would tell a ton... Mine have been posted before.. I look at 2.5plots all the time...

I know of a consistant 120mph 2.5L Omni that shifts by 5500 or so... Making in excess of 350 whp. This guy is an excellent driver...

My point is.. I don't chime in on threads about "how high can you turn up the boost on pump gas" any longer. my car was set-up right and could really turn the wick up. People reading my post would only read what they wanted to and ruin their engines. (another "aged" (hehe) forum contributer pointed that out to me and he was right)

Your car is also an anomoly... 99% of the people would be disappointed with their 2.5's if they expected them to run as high (lol, its a relative term for our cars ) as 5700 rpm for shifting.

[GLHNSLHT2]

Quote:

Originally posted by glhsken GLHNSLHT2 I'd really like to see a dyno plot of your engine. That would tell a ton... Mine have been posted before.. I look at 2.5plots all the time...

I would like to see a dyno plot on my motor as well. I just haven't gotten around to it. The timer at the track makes a pretty good thing to figure out what shift points make my car run it's fastest. It taught me that I should be shifting my 2.2 at 5200rpms rather than the 5800-6000grand I was trying when I first got it. When I first went to the track with the 2.5 I tried 5000rpm shift points under the thought that I've read everywhere about 2.5's not liking to rev which made sense. Car was negative boost creeping between 12 and 11psi. But big deal it was only over 1psi. The car went 14.6-14.9 that day. I was a bit dissapointed with it considering how much stronger the motor felt over the 2.2. I thought about it a bit and decided to try higher shift points. I worked up slowly a couple hundred rpm a time. The same time I had worked the boost up to 15 on my way back and forth to work. At the track it would creep from 15 at 4000rpms down to 11 at 5000rpms. I kept shifting higher and higher that day and found 5700rpms is what I went quickest at. I tried shimming the wastegate and it would creep down to 11psi just the same every time. After getting a new turbo with a big can wastegate I tried changing my shift points lower again. It still likes the 5700rpms. There's been 1 time since I started running 13's when it didn't like that rpm. I actually had to shift at 4800 rpms to get it down to a 14.1. The lifters were toast and didn't like the 15w50 M1 I was running. My theory into it is that the valves weren't opening as quickly or as fully as they should have. At the same time it had also stopped compensating for the amount of fuel I was throwing at it at idle. A swap in lifters with a bleed hole in the top of them quickly had the computer being able to compensate for the fuel at idle again and the high rpm power was back as far as what I felt in the seat of the pants but I haven't been able to get back to the track to test it.

Quote:

I know of a consistant 120mph 2.5L Omni that shifts by 5500 or so... Making in excess of 350 whp. This guy is an excellent driver...[/b]

That works great for him. If that's what get's him down the track the fastest great!

Quote:

My point is.. I don't chime in on threads about "how high can you turn up the boost on pump gas" any longer. my car was set-up right and could really turn the wick up. People reading my post would only read what they wanted to and ruin their engines. (another "aged" (hehe) forum contributer pointed that out to me and he was right) [/b]

I've only given examples of what my car has done so that people will try different things from what everyone else out there has done. Keep them thinking. My 2.2 would crank out 18.5psi on the stock fuel system. I wouldn't of tried it if I had believed everything I had read about where people would add extra injectors at or gotten RRR's with AFPR's and bigger injectors. Gus Mahon wouldn't of gone as fast as he did in his Caravan if he had believed everything written in the 2.2/2.5 FWD handbook. So far I'm only running 13.5 on this setup. Just under cutout.

[/quote]
Your car is also an anomoly... 99% of the people would be disappointed with their 2.5's if they expected them to run as high (lol, its a relative term for our cars ) as 5700 rpm for shifting. [/b][/quote]

From what I've seen yes I think my car is different from what everyone else's is. If you see pics of my engine bay there's an obvious difference when you compare it to 99% of all the other 2.5's out there. Is the visual clue the reason it revs up so good? I don't know. But it's the main difference when I see almost every other 2.5 out there. Basically people need to get out to the track or dyno and see what their car likes. Watch the gauges (that should be a fricken no brainer) and experiment a little. Sometimes you have to blow stuff up to learn things. But people should never stop re-evaluating their setup or their driving style. Another example of that is I had the lower I/c hose off one day while messing around with it for some reason which I can't remember. I reached over and revved the motor by hand and the turbo blew off the hat that I was wearing. So I brought the rpms up to about 3grand or so by ear and just held it there. Hmmm ok it's not blowing near as hard as when I just blipped the throttle. So I revved it from idle to 3kish a couple times. Whoa! I blew nice and hard again. This caused me to re-evaluate my launch technique which had always sucked. I would either spin the snot out of the tires or bog hard. I had always just tried to hold the rpms in one spot, just like I had done on my dad's 1970 911S which loved the clutch dumped at 3200rpms and would let the rear weight bias do the rest. The next time at the track instead of holding the rpms in one spot I went from zero throttle to WOT as fast as I could while keeping the rpm around what I wanted to launch at. It instantly improved my consistency in getting off the line. Once in a while I'd spin the tires pretty good. I re-evaluated this too as I would just try to slowly back out of the throttle to get them to stop and then shift at whatever shift point I was using at the time. I threw that out the window one day for some reason and backed out of the throttle enough to make them hook at 4000rpms. As soon as they grabbed I grabbed 2nd gear. Anyway I'm always rethinking things. reading what other people have done and trying it if I think it's plausible. When I get a chance to get to the dyno I'll post the results. But for now I'll continue to use the track as my gauge on where I shift.

Later