Quamen

iTrader: (14)

As many of you know there has always been the question about switching to something like a Q45 TB (90mm as compared to 70mm) with a cable setup. However it always comes back as an expensive process that ultimately in the end require the use of a standalone ECU.

Here are the issues as I see them.

-When you switch cable TB you eliminate the TB which means that the ECU no longer thinks that it has a TB attached (no resistance in the curcuit) and there is no TPS signal. The TPS signal is not a big deal because as long as the cable TB has a TPS sensor with the same voltage output the stock ECU should be happy. You could wire a resistor into the curcuit in order to simulate a TB and keep the ECU happy but I think that there is a better use for it.

-Idle control is another issue. Cable throttle bodies have a IAC (idle Air Control) valve which gets a signal from the ECU in order to maintain proper idle by allowing air to bypass the TB. I think that I have come up with the solution for this issue and it is as follow:


Here is my proposed solution.

First, in the solution that I am going to describe you must assume that you have an oil catch can that is routed some other way than to the PCV nipple on the intake manifold (front passenger side of the manifold). Say you weld a nipple onto the intake tube somewhere else and just run the hose there instead.

If you look at the lower plenum there is a zinc plated piece of sheet metal that is held onto the center section bu some bolts. This covers the PCV scavenging area. In this area there are small holes which go into each runner to help draw air out of the crankcase. After the sheet metal is removed you can see that if you were to machine the two center bolt platforms lower you would be able to weld in a piece of metal to close this area up completely similar to the orignal purpose of the stock zinc plated piece (this may even be an unecessary process). So now you basically have a chamber that allows air into each cylinder

Now if you were to take a servo motor with the same resistance as the stock TB motor and make a mini TB for a lack of better terms and put it in line (run a line from the intake pre-TB to the PCV port) you would essentially make the ECU think that it is controlling the stock DBW TB. And since the stock ECU used the stock DBW TB to control idle what you essentially have is a IAC valve!!!

The only thing is that you would have to calculate how much CFM the engine need to maintain a certain RPM and determine if the PCV port can even flow enough CFM to maintain a decent idle. Otherwise you can just weld a nipple of the needed size anywhere on the manifold post TB.

I think this could be the answer to the cable TB conversion that has been plaguing so many people.

Please give any input that you can.

Quamen

iTrader: (14)

One of the only problems that I could really see happening would be if the ECU was smart enough to see that idle was being adjusted yet the TPS signal was not fluctuating since it would be recieving it's TPS signal from the cable TB.

However, maybe the stock ECU would try to open the TB to increase RPM and by the time it realizes there is no TPS fluctuation the idle needs to be lowered so it would want to close the TB and would continue to just cycle without faulting or possibly just through a CEL and not go into limp home mode which would be exceptable since many FI guys have a CEL to begin with.

Audible Mayhem

iTrader: (48)

there is still a TPS signal, 0-5 volts, the conversion would be easy.


fine tuning it should be fairly easy as well

Quamen

iTrader: (14)

^^^
So could this be the solution?

Quamen

iTrader: (14)

No more input from anyone?

If this would work this would open up the door for an ITB intake manifold that is cost effecient.

Quamen

iTrader: (14)

Anymore input?

rocks

iTrader: (1)

The only reason you need and IAC is during cold starts. You can do without it but you will have idle up the car higher to like 1k rpms untill it warms up. If you read through the megasquirt stuff it tells you about it and what happens without it. It is very possible to do it without an IAC.

Here is some reading about IACs, hopefully it will help you out some, http://www.megamanual.com/ms2/IAC.htm

Quamen

iTrader: (14)

^^^^
I don't think this applies to our cars as if this was the truth then most people would not have loopy idle when they just get bored out TB's.

LHP

IAC's are for adjusting the idle to compensate for things like AC,
which takes a bit of power to run.
Also for auto trans while in gear at idle etc,= (idle air control).

Get in touch when you want to start designing that ITB system.

LHP
www.haywardperformance.com

THE TECH

iTrader: (154)

Interesting. Not sure if the gains would necessitate all the work involved.

rocks

iTrader: (1)

ITBs usually provide a pretty big gain. People probably have a lopey idle from a bored throttle body because air is going past it at idle. But yes it is possible to get rid of the IAC, you will just have to use a higher idle to compensate for things like turning the A/C on and the fast idle from a cold weather start.

LHP

It all comes down to what the end user wants,
and or if they are racing in a particular class that requires being NA or not.

Generally with ITB's you can run much more aggressive cam profiles and still have good drivability/throttle response.

An example: S2000 Honda customer, stock 2.2 litre engine approx 200hp to wheels,
With good exhaust system/header,my 50m/m intake system and some custom cams to take advantage of the intake system,
200 lbs torque/ 275 hp out of a stock engine with just the cams internal change.

Not all engines will respond this way,
but it shows what can be done with the right parts.

I have done cylinderhead and lower intake manifold work on the VQ35 engine,
and they are a nice package,
and I can see a reasonable gain if some one wanted to get aggressive.

LHP
www.haywardperformance.com

Quamen

iTrader: (14)

Thanks for the input everyone. This would be more intended for FI if anything to increase response.

Chebosto

iTrader: (43)

throttle responsiveness can be pre-programmed via Reflash.

ACEMAN

iTrader: (29)

My only question here is.

Is there not a drive by wire throttle body that is larger that we could make a adapter plug for? Dont they all use the same amount of wires to control the butterfly? You might have to have a adapter plate made, but if it is just a simple wiring plug change.

Why would this not work??

Later
Todd

ACEMAN

iTrader: (29)

Found a link for one used for the LS1

LS2 to LS1 Throttle Body Adapter Harness






http://www.lmperformance.com/7688/68.html

Later
Todd

ACEMAN

iTrader: (29)

Looks like the NSX is using a Q45 throttle body as a upgrade. Nice gains close to red line.

http://www.gt-rom.net/gtrom/index.htm

Will need babelfish for this site http://babelfish.altavista.com/

Im bored at work

Later
Todd

Quamen

iTrader: (14)

I think that I may have come up with a good solution that will allow me to make DBW ITB's.

Quamen

iTrader: (14)

I could easily come up with a solution that could be put on something like the Kinetix SSV but I don't know if that is the direction that I want to go for a couple of reasons.

I can make a plenum out of billet with ITB's that is setup for DBW but the problem lies in fitting the motor for the TB. This leads me to believe that the best route would be to make some sort of linkage that attaches to the DBW setup. I don't think that I could get the motor low enough to go under the y-collector if I made it part of the manifold. If I went to the side with the motor I have issues with the fuel rails and if I go up with it I have issues with the inlet or I have to decrease plenum symetry.