Hey,
I'm planning on putting a TBI system on my suzuki samurai engine, which is currently using a carburettor, and so has a very small plenum volume (if any really). What problems is this going to cause with a TBI bolted straight on? I have seen photos of engines set up like this but can't see it working well.....? I'm thinking I'm going to have to add some volume in there somehow, correct?
TBI on a carb manifold
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
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Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
Re: TBI on a carb manifold
Putting a TBI on a carbed manifold usually works out OK. About the worst that may happen is that the fuel distribution is rarely ideal, and it may be a bit rough on a cold start until you get good fuel vaporization. Putting a TBI on something with a port injection sized plenum probably would not work out very well actually,
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Bernard Fife
- Master Squirter
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- Joined: Thu Oct 29, 2009 12:54 pm
Re: TBI on a carb manifold
hedgeboar,
I have done this, it works fine. Both TBI and carbs require 'wet-flow' manifolds.
The plenum has two main effects - it smooths the manifold vacuum spikes from the valves opening and closing, and it smooths the air flow through the throttle so the net air flow is greater. However, a smaller plenum with a larger throttle sees the larger vacuum spikes and uses these to meter fuel more efficiently. In the case of TBI with a small plenum, you don't need a large vacuum spike to draw fuel from the venturi like a carb. But you might need to use a 'damper' on the MAP sensor line to get a consistent signal, as described here: http://www.megamanual.com/v22manual/mtune.htm#trouble
Port injection doesn't generally use a wet flow manifold in a OEM application, so as Matt says a TBI on a port injection ('dry flow') manifold wouldn't be a good idea.
Lance.
I have done this, it works fine. Both TBI and carbs require 'wet-flow' manifolds.
The plenum has two main effects - it smooths the manifold vacuum spikes from the valves opening and closing, and it smooths the air flow through the throttle so the net air flow is greater. However, a smaller plenum with a larger throttle sees the larger vacuum spikes and uses these to meter fuel more efficiently. In the case of TBI with a small plenum, you don't need a large vacuum spike to draw fuel from the venturi like a carb. But you might need to use a 'damper' on the MAP sensor line to get a consistent signal, as described here: http://www.megamanual.com/v22manual/mtune.htm#trouble
Port injection doesn't generally use a wet flow manifold in a OEM application, so as Matt says a TBI on a port injection ('dry flow') manifold wouldn't be a good idea.
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it.” - George Bernard Shaw
Re: TBI on a carb manifold
OK cheers that's good to know. How many injections per ignition are/were you using lance? Would I be correct in assuming that it would be best to maximise this while keeping the pulse width at idle at an acceptable level?
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Bernard Fife
- Master Squirter
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- Joined: Thu Oct 29, 2009 12:54 pm
Re: TBI on a carb manifold
hedgeboar,
I can't recall how many squirts I used (this car has been gone for at least a couple of years - it was my beta MicroSquirt test vehicle), but I do remember experimenting with both the number of squirts and the injection start to get it to run the best (this took less than an hour). I suspect I ended up at 4 squirts/alternating.
Lance.
I can't recall how many squirts I used (this car has been gone for at least a couple of years - it was my beta MicroSquirt test vehicle), but I do remember experimenting with both the number of squirts and the injection start to get it to run the best (this took less than an hour). I suspect I ended up at 4 squirts/alternating.
Lance.
"Never wrestle with pigs. You both get dirty and the pig likes it.” - George Bernard Shaw