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RX1 Bender Stage 2 Install Manual


Feb 27, 2022
2003 RX-1
Newbie here and I have been searching this forum for any information I can gather on the Bender turbo kit. I just purchased a 2003 Rx1 with a Bender kit installed and I am having issues with the sled backfiring and not wanting to climb over 3k. I currently have the carbs off and are cleaning them. I am looking for any information pertaining to jet sizes or differences in the carbs from a stock one that I need to check. There is a vacuum switch on the dash that runs back to the wastegate on the turbo. I am assuming that is the boost controller?? Any documentation on the turbo or even an RX1 service manual would be appreciated. This forum has been super helpful already ,but I am not sure how active it is on the almost vintage RX1 platform:)

Backfiring usually indicates an exhaust leak. Yes any lines plumbed to the wastegate are going to be for controlling it. Do you know the health of the engine? Compression or leakdown? How many miles on it?
The sled has 3500 miles on it and I did a quick compression check on it and I'm getting 110 lb per cylinder cold.
One way to check for exhaust leaks is to start the engine and then use a shop rag or something similar and plug the two rear exhaust pipes to see if it stalls. It should sputter and eventually die but if not, then you have an exhaust leak. Wouldn't think with the miles but those four exhaust donuts on the flex joints were known to wear prematurely.
How hard are those joints to get too? I assume they are under the gas tank?
Yes under the gas tank and a PITA. Figure a solid few hours, I struggle most with the bracket that is riveted in the tunnel that holds the y-pipe. Remove the flex from the head and see if you can remove the the pipe that way and leave that header 4-2-1 pipes alone. You may want to drop the suspension and check the exhaust. They are thin wall and crack easily in many different places. Happy to finally pitch mine and use the dump off the turbo on my twincharged.
All right the latest update: I got my carbs back from the dealer and they went through them cleaned them and recorded all the jet sizes. Everything was set as stock except the air jet was 140 instead of 120. I installed them tonight and put everything back together. It started great and idled perfect for about 30 seconds then the rpm began to climb to 2500. If I choked it for a quick second it would drop back down. When I revved it up it would hit 4k and just hang there like a rev limiter was on. A couple things I have ruled out:
~The TORS is bypassed
~New plugs
~Coils cleaned and greased w/ dielectric
~I changed the oil because it was full of gas from running rich. I ran it for about 3 mins and the new oil already smells a little gassy?
~What should my fuel pressure be with the electric pump and what inside the carbs would stop the electric pump from overfilling the bowls? One of my thoughts is that it is running way too rich. When it cuts out at 4k it sounds similar to trying to go wide open with the choke on. I am just not sure why it is running so rich.

Any Help would be appreciated.
with carbs fuel pressure should stay around 7 psi.
with carbs fuel pressure should stay around 7 psi.
I checked them yesterday and I'm getting 4 lb s. I pulled the carbs and cleaned them once more and got it to idle without climbing but still will not climb over 4,000 RPM. It sounds like it hits a rev limiter right at 35 to 4,000 RPM.
It's highly likely its because of how the diaphrams are opening the carb slides unevenly or not enough, you either have one or more diaphrams leaking or have a boost leak probably at the little T's with o-rings between the carbs for the throttle slide diaphram vents that will be plumbed to the IC plenum to see boost. Best way to check that is remove the IC so you can view the throttle slides, then rev it up and see if they open evenly.
Next take a small air regulator and pressureize that vent line from the IC to the throttle slide diaphrams, just 1 or 2 psi will cause the slides to open as they work on a pressure differential. If they don't open evenly, start tracking down air leaks.

The float bowl vents should be plumbed to the pitot tube in the front charge tube near the oil tank so the bowls see boost and are "equalized" to prevent the fuel from being pushed back down the jets into the float bowls when the boost starts and cause it to starve for fuel.
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I looked at all the slides when it was running and verified they all were opening at the same time. Everything looked good. I then put some air pressure on the carb vent line and the first two carb slides opened but the second two did not move. I was convinced it was because of a loss of pressure before it got to the second 2 carbs. Gas was blowing out the front of the carbs. I then idled the engine and sprayed carb cleaner over the intake boots and it bogged down on carb #3. After re-tightening the carb boots and applying grease over the carb 3 boot I started it and it immediately picked up to 9k before the leak presented itself again. So fingers crossed it is just the intake boot with a small air leak. Mbarryracing thanks for putting me on the right path.
If the carb slides don't all open at the same rate and evenly when you apply shop air to the vent lines, that will make it run like crap. Keep eliminating leaks until all 4 slides open evenly when you apply pressure to the vent line.
The latest update: I dropped the track and checked the boost tube, exhaust and also checked the exhaust manifold for leaks. Nothing visually found so I also pressurized the exhaust and boost tube and didn't find any obvious leaks. After going through the carbs multiple times I bought 2 billet tees from Jannetty Racing to try. I am hoping that is my issue. Through this process of taking it apart multiple times I must have found some leaks because I can now get it to climb to 7k every now and then. At what rpm should I expect to start seeing boost with the rear mount turbo?

Thanks for all the help and I will update as I continue.


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It should rev to 10k on a jack stand, but you won't see any boost because the engine is not loaded down enough. Riding it you might not see boost creep up until over 1/2 throttle, depending on how soft the wastegate actuator spring is.
The billet T's are a huge improvement over the stock plastic T's with o-rings that leak. Focus on leaks around the throttle slide diaphragms and where the carb halves (front and rear at the throttle slide bore) come together. If you have one leaky diaphragm from corrosion buildup that slide won't open evenly with the others and that cylinder won't make power, will limit your RPM like a dead cylinder.