I finally installed the Stillen y-pipe and the Courtesy B-pipe. First impression without having been able to put many miles on them are good. The sound is a much throatier growl (sounds great!). Performance-wise, it is awesome! It really hauls! In combination with the JWT ECU, the thing really snorts from about 3500rps and up. Again, I really haven't had a good chance to really flog the thing, and the ECU still has to adjust, but I love it. It just feels so much smoother now, and the rpms have really dropped at cruising speeds, so my mpg should increase. As far as the Stillen Y-pipe goes, it seems very nice. It has a little bit of a hissing noise at WOT, but other than that, I think they resolved the "bees in a can" syndrome. Well worth the money, in my opinion!

Peace-

 

How can RPMs drop with a mod? It's not like you modified the transmission gears or changed your wheel size, right? My brother told me one time that his friend said that when he switched to synthetic oil, his RPMs at highway speeds went down. I never understood that. How can that possibly decrease RPM's at a given speed in the same gear?

 

Yeah RPMs should not drop. You may have gained some torque and find yourself not having to rev as much before shifting.. But the RPMs won't drop at speeds.. 60mph will still be the same RPM as it was before.

ZuM

 

If you look at a hp/torque dyno that has significant gains, the go-power provided at 4000rpm "stock" would come earlier in the powerband on a modified car. So wouldn't the speed that the stock engine hit at 4Krpm would come at a lower RPM modded? Isn't this where the mileage gains come from?

[Edited by philpoe on 01-17-2001 at 10:27 PM]

 

[QUOTE]Originally posted by philpoe
[I]If you look at a hp/torque dyno that has significant gains, the go-power provided at 4000rpm "stock" would come earlier in the powerband on a modified car. So wouldn't the speed that the stock engine hit at 4Krpm would come at a lower RPM modded?

Nope.Just because you have more HP does not meen your RPM's will be lower then before.More HP at a paricular RPM will just make it easier to exelerate at a given RPM.For example a 1000HP nissan Skyline can't go say 80 in first because it has a 1000 HP.I hope you get it.

 

RPMs is directly related to gearing. Say the top of 1st gear is 35mph. Its the top of first gear well.. because you're at 6200rpm or whatever redline is.. And its bouncing off the revlimiter. No matter how much HP you gain. You will not be able to bust past the rev limiter. The top of 1st will still be 35mph. No matter how much HP you gain, you will not be able to bust past the top of 2nd gear.. etc.. etc. Unless you change the redline or the gearing (transmission or tire size), the RPM/MPH relationship will be the same. You'd still be around 2k rpm or whatever in 5th gear at 60 even if you had 1000hp. Anyone wanna try to give a better explanation? I think this is a pretty important concept..hehe..

ZuM

 

It makes sense to me that, if an engine doesn’t have to work as hard at crusing or idle speeds, the RPM’s would be lower.

I don't know about bouncing it off the rev limiter, though...

I know when I had my 280zx and my ZX2, when I turned on the A/C, I could watch the tach go up a little because the engine was working harder.

Just a thought...

 

The ratio between the engine speed and the speed of the wheels is locked. for example, if the ratio was 2:1 in 3 gear, say, the engine crank would spin twice, and the wheels would spin once. There's no way to change this locked ratio without diff/tranny mods.

Think of a BMX bike. It has NO gears, jsut one set ratio between the pedal crank and the back wheel. If I got on it and started going 30km/h, I'd maybe be turning the pedal crank at say, maybe 50rpm. If Sylvester Stallone (who has much more powerful legs than me) got on the bike and started going 30 km/h, He wouldn't be pedalling any slower than me, would he? No, because the ratio remains the same.

 

and purchase the professional trasmission gear on any car
you will see that when your car is with stage 1 turbo, 1st gear you can only get X mph at Y RPM
when you get stage 4 turbo, you still get X mph at the same Y RPM...
ok..
problem solved
although I do have this going with my max...I am cruising on a 'level' street and my rpm stays at a certain number and my speed needle goes up...
humm....Heavy wheels? Draggy car? must have been one of those...anyhow...

 

Incorrect. The RPMs go up when you turned on the A/C because the ECU raised the idle speed to compensate so your car wouldn't stall. You telling me if you had 10000hp, you can go to 100mph at 1000rpm? I don't think so.

ZuM

 

I agree that the speed would stay consistent w/ same gear ratios and added HP. But would this be true of an automatic also as opposed to just a 5 speed? B/c in my Caravan if I'm on the hwy going 70 and touch the gas the rpms will jump 2-300 rpm w/o it shifting down and w/o the torquye converter letting go...

 

Hmm, well in an auto tranny. The torque converter doesn't lock till you hit 4th gear and a constant cruise speed. So what's probably happening is the tranny slipping a bit because the torque converter hasn't locked up. But RPM is still pretty relative with speed. Auto or 5-speed.

ZuM

 

I had my Y pipe done and I didn't notice a drop in RPMs. If there isn't a drop in RPMs and the engine is working the same as before, then how does the car get better gas mileage? Or is that an advertising trick to fool people into buying the product?