Board logo

Bike Carbs as Throttle bodies
davidimurray - 3/1/18 at 12:36 PM

Happy new year everybody. Not been on here recently as the car hasn't been used for the last year due to a house renovation. But the brain is now running wild with project ideas.

At the moment I'm running a Duratec on ZX6R bike carbs. I want to go to fuel injection, but by the time you add throttle bodies, ecu etc things seems to be expensive.

Then I stumbled on Speeduino - which is looking like an interesting and cost effective solution to the ECU side of things. That leaves me with the ITB side of things - then I thought. Why not refit the injectors into the Duratec head(along with new pump regulator etc), disconnect the fuel from the carbs and use them as ITBs. I know it won't be perfect or unleash the full potential. But it would mean I can do half the job now and then fit ITB's when I can afford them.

Anyone tried this?

Cheers

Dave

SJ - 3/1/18 at 01:05 PM

I'd considered doing exactly the same. I can't see any reason why it won't work. Would you retain the slides or just rely on the butterfly?

davidimurray - 3/1/18 at 01:23 PM

In theory - the simple version would be to retain the slides as I guess they add a restriction at low throttle openings, but would be easy enough to whip them out and see if there is any difference.

kingster996 - 3/1/18 at 02:48 PM

I think you'd be better off just fitting bike ITB's and selling the carbs.

Basically, to get the best out of it you'll need it mapped properly on a rolling road - cost £2-300. If you swap the carbs for bodies later, then it's another £2-300 to get it mapped all over again.

Why do that when bike ITBs can be had for £100-150? (less what you get for the carbs)

davidimurray - 3/1/18 at 03:23 PM

quote:
Originally posted by kingster996
I think you'd be better off just fitting bike ITB's and selling the carbs.

Basically, to get the best out of it you'll need it mapped properly on a rolling road - cost £2-300. If you swap the carbs for bodies later, then it's another £2-300 to get it mapped all over again.

Why do that when bike ITBs can be had for £100-150? (less what you get for the carbs)


I had thought about this - but by changing to ITB's it would also involve a new manifold so probably another £100. Depending on the ITB's chosen I would probably need to re-space and make a new backplate for my cold air feed. In terms of mapping my plan was to do it myself while it was 'sub-optimal'. I have my current ignition map and a target AFR table for the Duratec and also already have a wideband.

As crazy as it sounds my thoughts were I could probably do bike ITB's now for £300 or have some Jenveys for £800 later. This is definitely not the best solution but a stepping stone. I had originally been put off the idea due to ECU costs but having seen the Speeduino it's got me thinking!

Out of interest have you got any experience of good cheap bike ITBs/recommendations?

Thanks

Dave

kingster996 - 3/1/18 at 07:37 PM

My setup is a bog standard crate 2.0 Zetec with GSXR1000 throttle bodies and a DanST inlet manifold, runs off a DTA s60 Pro and mapped by JDM Dyno see printout below.

But at 183bhp and 175ftlb of torque, it's pretty good for a standard lump - so can't see why anyone needs to spend more on Jenveys IMO

Description
Description
Description
Description
dyno run
dyno run

The DanST manifold is lovely. Really well made and matches the ports very well.

rf900rush - 3/1/18 at 09:21 PM

I am collecting parts to do a budget megasquirt system for a Suzuki g13bb car engine.
I managed to get two sets of Yamaha Fazer 600 ITB's for £60 for both sets.
The only bit I did not get are the inlet rubbers.

May be a bit small for a 2l car. but if you keep away from the GSXR1000 / Hayabusa ones there are
some bargains to be found, Not that a set of GSXR ITBs are not exactly expensive for what you get.

SPYDER - 3/1/18 at 10:33 PM

As an interim measure the bike carb solution will be fine. I suspect that you will have to remove the slides ( or fix them at max opening ) in order to get a valid MAP reading. If you leave them in the MAP value will essentially stay static. Having said that you may have to run AlphaN algorithm anyway, but you will still need an accurate MAP signal to reference your fuel pressure regulator to.
The Speeduino can be tuned using TunerStudio as per Megasquirt. Buy the paid version. The VE Analyze Live (VEAL) feature is very good and will get you a good tune if you use it right, and assuming that you have fitted a decent wideband lambda sensor.
A rolling road session would be on the cards following your planned step up to GSXR bodies but may not be necessary in the meantime.
My own GSXR equipped car running MS2 has been tuned solely using VEAL with the exception of a few tweaks to the ignition table when checked out on the rollers.
Keep us posted with the Speeduino side of things.

davidimurray - 4/1/18 at 01:50 PM

Thanks everybody for the advice/comments. I am getting very tempted now......

fazerruss - 4/1/18 at 09:14 PM

quote:
Originally posted by kingster996
My setup is a bog standard crate 2.0 Zetec with GSXR1000 throttle bodies and a DanST inlet manifold, runs off a DTA s60 Pro and mapped by JDM Dyno see printout below.

But at 183bhp and 175ftlb of torque, it's pretty good for a standard lump - so can't see why anyone needs to spend more on Jenveys IMO

Description
Description
Description
Description
dyno run
dyno run

The DanST manifold is lovely. Really well made and matches the ports very well.



That's decent power you're getting. Could you give some specs please as I have the same engine and plan to fabric from scratch my own throttle bodies and manifold.
If poss could you give me the throttle body diameter and manifold diameter, manifold length and trumpet length please.

Cheers

SPYDER - 4/1/18 at 10:27 PM

^^^^^ That's not just pretty good power. It's astonishing for a crate engine!

kingster996 - 4/1/18 at 10:40 PM

quote:
Originally posted by SPYDER
^^^^^ That's not just pretty good power. It's astonishing for a crate engine!

I know, it certainly surpassed my expectations. I was hoping for 175 at best.

Actually made 185bhp on first dyno set up, with 173 lbft. I swapped ecu (for several reasons) and second dyno run a year later was the one shown. Happy to swap the 2 ftlb for the 2 bhp

I did run it in from new using the hard and fast technique. Basically first 20 mins at 1500-2000 rpm then straight out and hard acceleration in 3rd to 6k and immediately off the throttle to hard decelerate. Repeated that several times to bed in the rings then drove fairly conservatively until it was mapped a few 100 miles later.

Seemed to work.

Edited to add: remember that dyno figures are for pub talk, what mattered to me was the way it drove after mapping. Also I used same dyno each time so I could compare. Other dyno might show different numbers.

[Edited on 4/1/18 by kingster996]

kingster996 - 4/1/18 at 10:54 PM

quote:
Originally posted by fazerruss
quote:
Originally posted by kingster996
My setup is a bog standard crate 2.0 Zetec with GSXR1000 throttle bodies and a DanST inlet manifold, runs off a DTA s60 Pro and mapped by JDM Dyno see printout below.

But at 183bhp and 175ftlb of torque, it's pretty good for a standard lump - so can't see why anyone needs to spend more on Jenveys IMO

Description
Description
Description
Description
dyno run
dyno run

The DanST manifold is lovely. Really well made and matches the ports very well.



That's decent power you're getting. Could you give some specs please as I have the same engine and plan to fabric from scratch my own throttle bodies and manifold.
If poss could you give me the throttle body diameter and manifold diameter, manifold length and trumpet length please.

Cheers


The throttle bodies are GSXR 1000 K1/K2. They taper from 42mm to 50mm. Trumpets are 90mm. Manifold is port matched, so 42mm at bodies and matches the Zetec at the head. I used Hayabusa injectors. Not sure what length the manifold is, maybe danst site will have info, but I was aiming for a total of 355mm from valve to trumpet end as I read somewhere that was ideal. Seems to suit it, so must be OK.

As I said on other reply, very surprising result, but remember dyno numbers are just numbers and only useful to compare the difference between runs on the same kit really.

fazerruss - 4/1/18 at 11:09 PM

Many thanks for this, it will give me an excellent starting point for the fabrication and machining.

hughpinder - 4/1/18 at 11:40 PM

Don’t forget you will need a high pressure fuel pump and return line too!

Kerrsco22 - 5/1/18 at 07:36 AM

i am currently converting from pinto to duratec he and have went a few different ways i bought a danst inlet for r1 carbs and a set of r1 carbs the guy i bought the inlet off was running it on a grass track racer using a standalone ecu to run the duratecs own injectors he reconed he was getting around 190 bhp out it tuned but said with more fettling would get more i have now got a hold of a brand new ecu through a guy in the club and now going full fuel injection my car is just a cruser and am not looking for a flying machine so happily gonna sit at the 150 mark if interested the carbs and inlet are for sale

fazerruss - 5/1/18 at 08:10 AM

quote:
Originally posted by hughpinder
Don’t forget you will need a high pressure fuel pump and return line too!


I've got the fuel line and injectors, rail ect that came with the crate engine. I need to buy a fuel pump and I will fabricate the tank with a built-in swirl pot.

SPYDER - 5/1/18 at 12:37 PM

quote:
Originally posted by kingster996
... I was aiming for a total of 355mm from valve to trumpet end ...


The graph below would seem to agree if you are aiming for 6.5 to 7K revs benefit and capitalising on the 3rd harmonic. Mine are exactly the same. Ideally we would have 2 foot long inlets!!




Your readout shows a little peak in torque at 5300 then a hint of one at 6300. These are probably be related to the inlet length effect.

Here are a few pics of my "airbox" arrangement if you can call it that. It's not perfectly sealed but it seemed like a reasonable solution within the space available.








Kerrsco22 - 7/1/18 at 08:01 PM

I am currently converting my tiger to duratec I have looked at the way you were saying running duratecs own injectors lot of grass track guys do it that way but use r1 carbs with the DAN-st inlet then I decided with ecu costs setups and rolling road costs I would just go the r1 carbs and my megajolt ignition which apparently gives around 175-195 bhp tuned properly then someone bought my megajolt so now am going down the throttle body’s with stand alone ecu and to be honest if I had costed it all properly I would have just swapped from twin 40s to the r1 carb and inlet route as plenty are running it that way with great results