Motorcycle Carbs on a Car

Bringing back from the dead. I recently found info that the R1 carbs have better flow than even Weber 45DCOEs, which is relevant to my interests since I want(ed) to put a pair of 45s on my (8v) GTI, and R1 carbs can be had as a set for $40-100 on eBay.

I know the pressures have to be greatly reduced, anything else?

Check if someone makes a manifold and linkage, unless you want to take a few months figuring all that out?

In reply to BoxheadTim:

Bike carbs usually mount by clamping a hose to them, so that part is pretty straightforward. Actually you could make a stub manifold for the engine and experiment with runner lengths easily.

That would be the plan... already have a DCOE manifold, and I would just weld some tube to some flanges and use that. I'd have to make a linkage no matter what I did. Perversely, it appears that bike carbs would be easier to do, since every Weber installation I've seen has some serious clearance issues against the firewall, bike carbs are typically a bunch shorter in length.

The nuts and bolts of installation doesn't bother me. I've done crazier/stupider. The thing that I am concerned with is the tuning aspects.

In reply to Knurled:

Fuel pressure and accelerator pump issues aside I don't think there will be many issues in tuning.

http://www.v-performance.com/articles/mikuni_carb_installation_and_tuning_instructions_.html

In reply to Knurled:

Tuning = MS2 and later with ITB mode enabled and lots of patience to get the Acceleration Enrichment correct.

Thanks for the link.

turboswede, the idea is that I don't want to spend a whole lot of money, so no EFI. Megasquirt isn't the low-buck easy button that it used to be.

+1 for mikuni, Decent part support and very reliable/easy to work with/tune/clean etc.

I have a motorcycle carb balancer/synchronizer if you need to borrow it in a couple years when this project gets off the ground.

In reply to EvanB:

Shush yourself. I'll have you know that I've made significant progress on the Quantum in the past few days.

Significant. Progress.

In reply to Knurled:

old MS1 + MS2 upgrade board = working solution for under a few hundred smackaroos.

Or you could play with buying jets, syncing carbs and rejetting when the whether changes.

To each their own.

Knurled wrote: In reply to EvanB: Shush yourself. I'll have you know that I've made significant progress on the Quantum in the past few days. Significant. Progress.

Is the engine put together yet?

EvanB wrote:

Knurled wrote: In reply to EvanB: Shush yourself. I'll have you know that I've made significant progress on the Quantum in the past few days. Significant. Progress.

Is the engine put together yet?

It's going into the car tomorrow, provided that I can lug the 016 out of the basement and into the Volvo's trunk by myself.

turboswede, my RX-7 has been on Megasquirt since 2008, this pictured engine is getting MS3-Pro and coil near plug ignition (much of the holdup was figuring out how best to work with the crankwheel I had to install), I'm very familiar with it. I don't want it for the GTI.

Heck, if I could, I'd put points on the GTI. It's been a long time since I've had a points car

Hooray!

I'm planning on carb for my next potential project (german powered by spinning triangles) but not motorcycle carbs for that. Unless it can be done?

I suggest using Yamaha RX1 sled carbs for a side draft car head,the last of the sport bikes that used the best CV carbs(the only type worth using imo)were all downdraft designs with forward canted engines.The carbs would need to be mounted on a steep angle for the floats to work properly and would look goofy,not likely clear the hood and offer no advantage as it needs to make the turn into the head anyways.

I used the RX1 carbs for a blow thru set-up with my AE86,pretty damn easy to tune and never gave me any weirdness.Sure more power could've been made with a megasquirt but I suck with electronic anything so this was easy to me in comparison.

[URL=http://s117.photobucket.com/user/kevlarcorolla/media/100_0801.jpg.html][/URL]

Only vid I have,this was the 1st time out with it and only running 8lbs.The beauty is no additional fuel tuning when bumping boot up or down with the auto compensation via the pitot tubes feeding boost pressure to the bowls to ramp fuel needs up relative to boost level.This is along with a rising rate malpassi FPR btw.I ran it at 12lbs after that and it would leave tracks with 225 r comps in 3rd no problem,made a goof with the boost controller one day and it pegged 18psi which the engine ran fine and ate it...T50 said uncle in one 2nd gear pull before I realized and lifted.

http://youtu.be/HjdvM3aS0TM?list=UUlj_qR5b5V96nv6ColmdMPg

I've run 39mm Keihin FCR flat slide carbs on my Datsun 1200 for several years now, both the A12 and A15 engine. One of advantages with them is being down draft (45 degree) is they clear the brake master cylinder whereas DCOEs would not. They also offer a performance boost over traditional butterfly valve type. Carbs like those on an FZR / R1 are CV style and so still have the flow restriction of the throttle shaft, if you can do them cheaply then it would be worth it. Whatever style is used the fuel pressure needs to be 2 psi or less, otherwise you'll over power the float needles. Most four stroke carbs have accelerator pumps so that won't be an issue. If you are running a car with a distributor, like I am, you will lose the vacuum advance. The Keihin FCR carbs have no enricher/choke so you need to pump the carbs several times on cold mornings. My car is a race car so not as much of an issue as it would be on a street car. For bike carbs with an enricher you'll either need to fabricate a choke cable or lift the hood pull the enricher knob start the car, let it warm a minute and then switch the enricher off......you'll wanna fabricate a cable. As for performance I picked up 18 hp over the equivelant DCOE equipped motor. Also anyone who tells you that the bike carbs are going to have a stumble "because that's how they are" doesn't have them jetted properly. On the subject jetting you will have to do the same set up work as with any carbs. I will pass along a couple of things, if you're using a cam with a lot of overlap you'll likely need to use a couple of step leaner pilot jets than one would expect. I needed to change the slide needles L1 dimension as the motor needed a quicker transitions from pilots to mains. FCR carbs make a whistling sound on part throttle when cold (my Beta motorcycle has a FCR carb and it does it too) and at idle you will hear the slides rattle a little as well. The FCR carbs do not suffer from starvation mid corner, the set I have was used on a Nissan A12 powered D-sports racer, whereas the stock CV carbs on my Yamaha powered D-sports racer suffered from fuel starvation in high G corners and the float bowls needed modifications to cure it. We are talking about cars that pull 2Gs so not likely to be an issue on a production car.

Tom

Knurled wrote: Bringing back from the dead. I recently found info that the R1 carbs have better flow than even Weber 45DCOEs, which is relevant to my interests since I want(ed) to put a pair of 45s on my (8v) GTI, and R1 carbs can be had as a set for $40-100 on eBay. I know the pressures have to be greatly reduced, anything else?

Have you checked out the Vortex carb/itb/sem section? There was a bike carb FAQ, and a ton of other info, in here. I was gifted a DCOE manifold shortly after buying my Golf and considered using bike carbs, after pricing Webers and Mikunis, when the main fuel pump died. I ended up replacing the pump and sold off the manifold to help pay for it.

Knurled wrote: That would be the plan... Perversely....

Your plan is rather dirty....

dunno if this link has been posted yet.

UK Classic Ford Mag Bike Carbs and old ford 4's article

This is the best info I have found when I was looking into this (I wanted to run a 302 with two banks of carbs into a GT40 lower intake...). I think they recommend drilling the jets out just a tad.

rcutclif wrote: dunno if this link has been posted yet. UK Classic Ford Mag Bike Carbs and old ford 4's article

Great link! I'm very interested in learning more about running bike carbs on my Datsun 280Z. This helped me get started.

chrispy wrote: Have you checked out the Vortex carb/itb/sem section?

No. I avoid the Vortex like the plague. Way way too high of a signal/noise ratio in the wrong direction.

Agreed, it takes some time to sort through the BS, but I found most of the tech sections and the motorsport section had good info if you dug deep enough. Just another reference tool, that's all.

In reply to M030 :

Do you still have a copy of the article? I want to put iTB's feom a motorcycle on my Triumph TR7.

If you do, can you email it to mr, billmeyer123@aol.com

Thanks!

I would like a copy too :)

I know on the Porsche 911 forum there have been a few threads on using 6 of them , I think off a modern Triumph bike , 

But then is it just as easy to get the trottle bodies off a newer BMW etc