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Jenvey ITBs | |
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By the winter of 2007-2008 I had had enough of the multiple small
problems with my current 45mm TWM ITB setup and was looking for an
alternative. I had been working with another member of my local
BMWCCA chapter that owned a 2002 and had installed a MS1-extra setup
with Jenvey ITBs. He had a year's worth of race and autocross
experience with them and had nothing but good things to say about them.
I had considered the Jenvey ITBs initially but I thought their cost was
too high for my budget. Now here I was ordering a set after
already buying the TWM setup just a year ago. I sold my TWM TBs to
a friend who wanted them for a race car. He did not care about
them sticking close to closed throttle, that's not where he would be
running them. I ordered a set of 40mm ITBs this time as well as the air horns, fuel rail, and the Jenvey throttle linkage which is a really well designed progressive linkage. I got rid of the TWM fuel pressure regulator and replaced it with a generic Bosch FPR. While I had my fuel system pulled apart, I added an idle control valve. The valve I used was the Bosch 3-wire "L" shaped valve used on many models in the 90's. This is a PWM type valve with +12V going to the middle terminal. If you ground one side terminal the valve opens, if you ground the other the valve closes. By pulsing the two side terminals the MS controller can vary the valve position. I fabricated a new vacuum distribution pipe out of 3/4 inch copper to accept the idle valve. The idle valve bypasses the TBs by providing air from the plenum directly into the vacuum pipe. The idle air then goes into the back of the TBs via the vacuum lines going to the distribution pipe. This is very similar to how BMW does it on their engines with ITBs. This page shows more detail about this setup. You can see the whole setup in these pictures. The FPR is mounted to the firewall just above the brake booster. The idle air valve is in between the end of the plenum and the vacuum pipe close to the firewall. The throttle linkage is mounted above the intake manifold over cylinders #3 and #4.
It took me a while to get the mixture and idle air valve setting correct but I can now start the engine with my foot off the gas at any temperature. The idle speed can be controlled as high as 1700 RPM and is set to maintain 1000 RPM when warm. The 40mm TBs are the perfect size for the engine. Throttle response and sensitivity are greatly improved over the 45mm TBs. I can take the engine up to 6500 RPM and still not see any reduction in the MAP signal due to the smaller TBs. I think I'm finally really happy with the hardware for the ITBs. |
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This site was last updated 12/29/09
