Raising Redline

[loesch8102]

What kind of engine work would someone need to do in order to achieve a higher redline safely. I know the maximum power output of my engine is at 6300rpm so it wouldn't really benifit all that much. But I would think whatever is needed to safely raise the redline would benifit the longevity of my engine in the long run.

[SilverY2KCivic]

Why the need to raise it anyways? Sure doesn't make you look cooler, that I can assure you.

Something like swapping out for a more agressive cam, and/or retarding or advancing the timing might allow for a higher redline safely, I'm almost sure you'd have to upgrade your rods as well just to handle the RPM increase and mose certainly your vale springs and retainers as anything faster than stock redline will induce valve float on stock components, which could permenantly damage your engine. But just keep in mind, you CANNOT raise the redline on an OBDII controlled car except by swapping out for say an EX model ECU, or a p28 ECU from '92-'95 Si hatchback, and with that ECU, you'd need an OBDII to OBDI harness addapter. Seriously, the trouble AND cost is way more than it's worth just to raise the redline.

[96HondaCivic]

Hmmmmm how about new valves and valve springs.
;0

[loesch8102]

SilverY2KCivic: Yeah, I know it's a dumb idea for the most part, but I wasn't necessarily thinking of raising the redline so I can rev higher. I was just wondering how to strengthen the internals so that the motor would be basically bullet proof so that I could, if I wanted to, run at 6000rpms all day without any worries. Basically I just want to be able to use the full potential of my engine whenever I want without fear. Right now I always shift before 3 grand unless I'm racing around with friends or something. I want to be able to run it hard.

[carrrnuttt]

FYI: Raising the redline DOES have many benefits, especially in a lower-displacement vehicle, and even more so in a car equipped with VTEC. With a higher redline, you can then raise the VTEC-switchover point.

Formula-One power-plants redline at about 13,000 to 16,000RPMs, depending on where they want them limited.

Motorcycles get their enormous HP-per-liter figures partly because of their sky-high redlines.

Lastly, achieving power in a modern internal-combustion engine can be simplified into this: Air + Fuel = Explosive force that produces power. More Air + More Fuel = More power. In a V8/high-displacement car, More Air/Fuel is achieved by having larger/more cylinders to burn the mix in. In a smaller-displacement motor, you can force more air and fuel in (FI) to achieve similar results, AND/OR you can also repeat the fuel/air explosion more times in a given period (Revolutions-Per-Minute) to achieve similar results.

• Read about torque-multiplication as it applies to manual-trannies.
• Read about torque vs horsepower.

To quote the author of that last article:
The Only Thing You Really Need to Know

Repeat after me. "It is better to make torque at high rpm than at low rpm, because you can take advantage of *gearing*."

[loesch8102]

Yeah, I totally understand what you're saying about F1 cars and things like that. But my engine was never designed to rev extremely high and therefore makes peak hp at 6300rpm and max torque at 5200rpm. So in order to keep max output to the wheels between shifts, it wouldn't benefit me to go above stock redline. After that limit I don't think the intake and fuel system can keep up.

[dirty91crx]

valve springs at least up top.....ported head for better high rpm air flow....depending on the engine upgrade the rods....my lil d15 is holding up to 8300rpm shifts. but also my head is able to flow the amount of air required to produce hp at that high an rpm along with a retarded cam timing as well as ign timing. im still on stock rods and they have been holding up well at 177whp and 136ft tq off the bottle....and 219hp and 174ft tq on the bottle all done shifting at 8300......stock valve springs will hold up for only so long and then.....your engine start floating valves at lower rpms and then it only gets lower as they weaken. i would say base your rpm limits on your tranny gearing.....you wanna maximize the use of tq and hp on what kinda gearing you have. i have a si/zc hybrid tranny in my car 2-3-4-5 are very close...while shifting at 8300 i drop to around 6500 in each gear.....there fore i need the rev limit set higher to make use of the gearing.....not so much a tq monster but a higher hp engine....im still tryin to come up with a good gearing for my engine as the tq #'s are high for the tranny as well as where max tq is made.

[loesch8102]

What does retarding the cam and ingnition timing do for you?

[dirty91crx]

retarding or advancing the cam timing moves your power band up or down. advance the cam and you get better acceleration but you lose on the top. retard the cam and you lose the accel and gain higher rpm power. advancing and retarding the ign timing basically does the same thing.

[JohnnyWash1]

Originally Posted by dirty91crx

retarding or advancing the cam timing moves your power band up or down. advance the cam and you get better acceleration but you lose on the top. retard the cam and you lose the accel and gain higher rpm power. advancing and retarding the ign timing basically does the same thing.

This is the common assumption, but not always true. The bottom line with engines is that each one is different, and each combo will react differently to modification. The idea is to find the perfect balance of parts that work in complete harmony. As for the cam timing, that simply determines the relationship between the rotation of the camshaft and the rotation of the crankshaft, i.e. the valves and pistons.


Jon