RX 1 MPI Supercharger Carb set up?

[Riceburner]

Looking for suggestions for Carb jetting sizes and set up for a Stage 1 MPI SC on 11 lbs from some of you fellas with old technology and or good memories or notes.

Or other suggestions if you think we have another issue.

Pertinent info:

Worked perfectly for 5 years as a 5-6 pounder . [22/26 pulleys]

Taken to Woody's last fall by a friend I sold it to for a head shim and switch to 10 lbs.

27 / 23 pulleys. 11 to 12 lbs of boost at WOT

Elevation 500 to 1000 feet. 4,600 miles on sled. Woody said engine perfect when he had it apart.

RPM 10,200 WOT

Holtzman silver springs I believe. We have the stock carb springs.

Idle AFR 11.2 cool, 10.4 hot.

50 to 60 MPH , 2-3 lbs boost, AFR 13.7 to 14.2

WOT AFR, 10.9 to 11.1

Sled stumbles, almost like kill switch hit when releasing throttle at 20 to 40 mph and AFRs go to less than 10.

TOR's has been defeated.

Goes like stink in a drag race but not trail rideable.

Woody did not make any carb changes when we went to 11 lbs of boost.

We think it has 140 mains in it and 17.5 pilots but not sure as we are just tearing into the carbs after getting everything else set up right.

TIA

Dave

 

[Sled Dog]

What do the plugs look like? I would think your going to need 165 main jets and 20 pilots for the extra boost.

 

[Riceburner]

Plugs look pretty good Rod.

She is way Fat not lean. Have a look at the AFR's again in my Query.

Makes no sense to me, but I think she needs jetting down.

I recall a fella a few years ago running a 20 lb Turbo using 127.5's if my memory serves me correctly.

 

[tjc]

do you have a bov? if so is it working?

 

[Riceburner]

Has a BOV / bypass. single Vacumn line

Does not blow off at idle but does when you burp the throttle.

Owner says it makes the sled worse when you back off spring pressure.

 

[Riceburner]

This one I believe.

 

[Cilius66]

What afr's do you run on the old RX1 and MPI compressor kit?

 

[Sled Dog]

Plugs look pretty good Rod.

She is way Fat not lean. Have a look at the AFR's again in my Query.

Makes no sense to me, but I think she needs jetting down.

I recall a fella a few years ago running a 20 lb Turbo using 127.5's if my memory serves me correctly.

Stock is 135's I would think with more air you need more fuel not less and with 10 lbs of boost the fuel needed would have to go up not down.

 

[Riceburner]

What afr's do you run on the old RX1 and MPI compressor kit?

Did not have a AFR guage or BOV when running 5-6 lbs.

She ran like a top though for years, no issues at all.

 

[Cilius66]

Plugs look pretty good Rod.

She is way Fat not lean. Have a look at the AFR's again in my Query.

Makes no sense to me, but I think she needs jetting down.

I recall a fella a few years ago running a 20 lb Turbo using 127.5's if my memory serves me correctly.

Stock is 135's I would think with more air you need more fuel not less and with 10 lbs of boost the fuel needed would have to go up not down.

I think I got 130 main on my 10 lb mpi, havent done alot of testing yet but the afr gauge looked okay. But I look after the same afr as I had on the turbo, maybe it should be abit different with thw compressor?

When you pressurise the carbs you also get more fuel through the jet.

 

[Ratpack]

I run 10lbs at 1000'-1500'. Stock shim. 135 mains and my afr's idle 13-14, slow cruise 13.3, wot 11.9-12.2. I tried 132.5 and it was to lean for me. That size may work at your elavation but 135 would be safer. You are way too rich. My first time to the mountains I ran 135's there too. The first time that I went 50 mph and let off the throttle I went over the handle bars when I saw 9 on the afr gauge.

 

[Cilius66]

I run at sea level and JE pistons (10to1).

Ratpack: Where do you have the needle in the carbs?

 

[Riceburner]

Thanks Cillius and Ratpack.

135's I think are stock although the local dealer told the new owner that the 2005 RX 1 LE had 140's in it when they looked up the specs.

You still running the 17.5 pilots and clip in third position.

I guess we will order the next 2 sizes smaller when we look at them tomorrow night.

Anyone else?

 

[jsjk-4-stroke]

i run 132.5 stock pilot , stock needel , at 7 1/2
no bov at sealeval , i get great milage and
wot at 11.4 af reading. would like to know where you have bov at it will not work on the intercooler it needs to be before the fuel signal which is down under in the allum. elbow . bov could also be a problem.

 

[Ratpack]

My needles are in the third slot. My bov is in the innercooler and works good now. You need to pick up the vaccum for the bov on the engine side of the carbs.