MX-3.com

okay, two problems actually....

first: when I start the car in the morning, it idles high(2500 rpm) and after the car warms up, it drops back to normal(600rpm ish) .

is this normal? it is kinda annoying with my loud exhaust setup.

also, it will do this if I let the car cool down for about half an hour.

is there a way to stop it from doing this?



second problem: it seems like it has lower power in the lower rpms, and at about 400rpmish, it really picks up. is this normal? it doesn't seem like a smooth transition. It seems like something is wrong. please help!

thanks

7

Problem #1: Not a problem at all, a very normal function of internal combustion engines. This is your automatic engine choke. When your engine is cold, it restricts the air intake into the air/fuel mixture. Thereby creating a "rich" mixture. This allows the engine to run when cold. If you've ever tried to start a lawnmower without using the choke, you'll see it's purpose.

Problem #2: If your rpm's really pick up at 400 rpm's, you're doing really well. I have a feeling you meant 4000 rpm's. The V6 has something called VRIS. I'm not completely familiar with how it works. I believe it's along the same line as the 4-Cyl VICS. This effectively changes the length and volume of the intake runners. This allegedly allows the engine to have a good comprimise of power between low and high rpm's.

Part of the cause of your loss of power could be your "loud" exhaust setup. If you've made your exhaust too free flowing by using larger pipes, or removing components, you may have greatly reduced the velocity of exhaust gases at low rpm's.

Low velocity exhaust gas = Loss of power

Good luck.

Ya I meant 4000rpms /me sheepish

my exhaust is just a big silly muffler, nothing else but stock stuff under there for now!

vris..... is this kinda like the v-tech that the honda people have?

also, could I turn down that automatice choking system, it is really annoying!

is 2500 rpms normal for when the engine is cold?

thanks again!

7

2500 rpm seems a bit high even for cold idle.

Should be between 1500 and 2000, irc.

But if it goes back to normal rpm when warmed up, I wouldn't worry about this too much.

The car does have a noticeable increase in power when the VICS opens, even when stock exhaust is used. My GS had a big silly muffler on it when I bought it as well and it was much more noticeable. The big silly muffler does add power at the top, but it really kills power at the bottom...making the transition more noticeable.

Go back to stock, you'll enjoy your car much more. Exhaust mods are not necesary or helpful until you start making significant changes in the engine.

VRIS only adjusts the length of the intake runners.

Long intake runners = better for low RPM
Short = better for high RPM


V-Tech has to deal with lift/duration of the cams.
the honda's have two sets of camshaft profiles. one with a lower lift/duration and one with a higher lift/duration

lower lift/duration is good for low rpm's. keeps things running smoothly, fuel economy ect. But high RPM's require a higher lift/duration, so the "V-Tech" simply "switches" over to the higher camshaft profile.

While the concept of adjusting the amount of air flow into the engine is similar, they're broadly different approaches, and I wouldn't class them the same.
VRIS has to deal with intake runners
VTEC is all valve timing and lift control.


That's just me, though.