VH45 plenum

[myndseye]

I know that the factory plenum's runners are tuned to help the motor make power around a certain rpm range. If you were to Maz out this motor to aid in spinning it faster, would not the intake start to work against you? I saw somewhere that one guy had his plenum cut down to get some hood clearance, but could cutting down on the plenum height affect its tuning point along the rpm range? What about ITB's as an option? I saw that someone was using them fabed up from a motorcycle application but they gave no detailed info it. Does anyone here know how this is achieved? I really have faith in this motor's potential, and I am choosing it to build my car around and I am sure I am not the only one looking to get everything out of it.
Modified by myndseye at 6:45 AM 10/27/2009

[kingkilburn]

If you want a quick look at itb do a search for KA itb. There are a few good threads around the web on GSXR itbs on KAs.

As far as the vh intake goes I think you would have to flow a heck of a lot of air before it starts working against you.

Maybe the GURU will chime in on this.

[Steve Lloyd]

I know that the factory plenum's runners are tuned to help the motor make power around a certain rpm range. If you were to Maz out this motor to aid in spinning it faster, would not the intake start to work against you? I saw somewhere that one guy had his plenum cut down to get some hood clearance, but could cutting down on the plenum height affect its tuning point along the rpm range? What about ITB's as an option? I saw that someone was using them fabed up from a motorcycle application but they gave no detailed info it. Does anyone here know how this is achieved? I really have faith in this motor's potential, and I am choosing it to build my car around and I am sure I am not the only one looking to get everything out of it.

Modified by myndseye at 6:45 AM 10/27/2009

zerothread?id=365444

That's the modified manifold, never heard back about how it performed though.

[Q45tech]

The length from the valve at mid opening to the plenum determines the rpm where the reflected wave arrives just before the valve starts to close and allows a finally puff of filling air. This puff can be 7-12 % EXTRA depending on exact rpm and air temperature.

This is why the VH acts like it is 8-12% larger in displacement as far a torque is concerned around 4,000 rpm.

Actually the plenum internal volume is less critical than interior runner diameter [it is tapered from plenum down to head] and it's length.

These are not very accurate but close to show concept:http://www.wallaceracing.com/runnertorquecalc.php

http://www.amsperformance.com/pdfs/intakemani.pdf

Remember torque for acceleration was the goal, HP for top speed was an afterthought in the Q45 design to match 4AT.

In 1990 hauling a 4300 pound AT car to 100 mph in 16* seconds was an accomlishment with a 274 ci engine.

* optimized JDM ecu not detuned for bad gasoline US version.

[Q45tech]

Every component from the air horn in front of condenser, air horn in front of MAF, length, diameter and volume of everything to the plenum was precisely designed to add torque at different rpms up to the 5,500 - 6,000 rpm HP peak design point. The slope of the torque decline from peak shows that everything is over sized not undersized.

Interesting to run dynos with different anbient intake air temps to see how precisely they worked for perfection. The tunning shows 2 HP peaks [5500 and 6,000 rpm] a 5750 rpm dip occurs that varies with temperature of air.

http://www.sengpielaudio.com/c...d.htm

As the EFFECTIVE length of tuning pipes can change 6.5% from 32F to 174F as can the rpm peaks and valleys.

[myndseye]

I see why you are the guru. Do you think it possible to get this motor to the plus side of 425 crank, revving around 8500? Preferably N/A. Let's assume money is no object, but also let's assume that I just wish that it wasn't.

[gs14racer]

i would definitly say yes, with some increased compression, and some good heads and cams ( like the ones i have for sale wink wink), plus some itbs or a short runner intake manifold, i would definitly imagine 350-370whp for sure.

The powerband will probably be peaky and short, the way i like it anyway.

[Mettler]

Cams, intake, revs... It'd be possible to get 100HP/L out of 10.2:1 compression wouldn't it?

[Q45tech]

Strip off the runners, plenum etc and it is just like any exotic 32V 4.5 liter race engine.Select the cams, match the heads, then design the runners, then plenum [single or dual]. Create some headers.

Obviously it is easier mathematically for the layperson to deal with 2 plenums and TB's since the body of technical work for four cylinders is easier to understand and use.

Few exotic engines {including NASCAR] make more than 84 lb/ft per liter on racing gasoline without boosting...........................HP is up to RPM

http://wahiduddin.net/calc/cf.htm

http://www.ret-monitor.com/art...s.pdfh ... valves.pdf