Individual Throttle Bodied TVR 5.0L with Megasquirt
Discussion
GreenV8S said:
in the meantime Peter, why not just run 8 MS units individually firing just one cylinder at regular crank intervals
Um, not sure if you're kidding or not!
it would do what you want though . just applying some lateral thinking.
or alternatively, why not have a special crank and cam ground so you can fire all 8 cylinders at the same time
Nice one Phil that looks sweet 
Do you see any issues with having so many throttle bodies, that when the throttle starts to open you suddenly get a massive increase in air flow? such that the butterfly angle vs Area open gradient is much higher??? could this cause surging (tip-in / tip-out) at small throttle opening?? or has my minimal understanding let me down?
How do you control the idle speed is this with a bypass or with the butterfly position??
Do you see any issues with having so many throttle bodies, that when the throttle starts to open you suddenly get a massive increase in air flow? such that the butterfly angle vs Area open gradient is much higher??? could this cause surging (tip-in / tip-out) at small throttle opening?? or has my minimal understanding let me down?
How do you control the idle speed is this with a bypass or with the butterfly position??
GreenV8S said:
Are those hoses reinforced to stop them collapsing?
Just a thought, these people have made manifolds for bike throttle bodies
www.altiss.com/automotive.htm
hmmm, well I chose the throttle size carefully so as they would still give me some control at low speeds and in traffic, a very clever freind of mine says they should be capable of flowing enough air for around 360BHP, so loads more than Im ever going to get out of this, but not too big so as to loss control. I guess now its simply a case of wait and see, I cant change it too much now
Phil
Phil
Seasider said:
why not have a special crank and cam ground so you can fire all 8 cylinders at the same time
Well if you're going to be like that about it I guess I could just take seven pistons out? It's quite rare to have all eight working together anyway ...
trackcar said:
in the meantime Peter, why not just run 8 MS units individually firing just one cylinder at regular crank intervals
Um, not sure if you're kidding or not!
it would do what you want though . just applying some lateral thinking.
or alternatively, why not have a special crank and cam ground so you can fire all 8 cylinders at the same time
I did think of a cam that would let me fire 2 cylinders at a time... Then I could have sequential injection with only a crank trigger...
Incidentally, I do have sequential injection running on mine now. It's a bit pointless at the moment, but it was fun to do...
Dax - it's all coming together now
Looks good! 
Getting a bit bored with all the naysayers on how sequential isn't worth doing.....
This is only the case if you don't change your injector spec from what it was on Batch fired, to get a gain in power your firstly need to reposition the injector somewhere along the inlet tract (ie no longer pointing at the back of the valve), Racing engines tend to have the injector just over the trumpet for this very reason.
Secondly you're trying to achieve open valve injection which usually means a much larger injector or fuel pressure to get it all in in time. This achieves a couple of benefits; one the tuning pulse is stronger due to the increased density of the charge (as its now cooler due to more fuel evaporation and the mass of the fuel along the entire inlet tract) Also you achieve control of the fuel timing in valve opening cycle which usually means you need overall less fuel injected (compared to batch fired) to achieve the correct in-cylinder mix and a more fuel efficent race car doesn't need to carry as much fuel and so is lighter etc.
The problems of achieving a power friendly sequential set-up are mainly that its not very nice to drive on part throttle (especially if your throttle is downstream of your injector) as the air-speed is too low and fuel drops out of the mix and forms puddles up down the port. And gets caught on your partly opened throttle etc.
In an ideal set-up you have 2 injector locations one conventional and one at the top of the port and you switch over at high throttle values.
It also helps emissions quite a bit but who cares about that...?
Matt
This is only the case if you don't change your injector spec from what it was on Batch fired, to get a gain in power your firstly need to reposition the injector somewhere along the inlet tract (ie no longer pointing at the back of the valve), Racing engines tend to have the injector just over the trumpet for this very reason.
Secondly you're trying to achieve open valve injection which usually means a much larger injector or fuel pressure to get it all in in time. This achieves a couple of benefits; one the tuning pulse is stronger due to the increased density of the charge (as its now cooler due to more fuel evaporation and the mass of the fuel along the entire inlet tract) Also you achieve control of the fuel timing in valve opening cycle which usually means you need overall less fuel injected (compared to batch fired) to achieve the correct in-cylinder mix and a more fuel efficent race car doesn't need to carry as much fuel and so is lighter etc.
The problems of achieving a power friendly sequential set-up are mainly that its not very nice to drive on part throttle (especially if your throttle is downstream of your injector) as the air-speed is too low and fuel drops out of the mix and forms puddles up down the port. And gets caught on your partly opened throttle etc.
In an ideal set-up you have 2 injector locations one conventional and one at the top of the port and you switch over at high throttle values.
It also helps emissions quite a bit but who cares about that...?
Matt
350matt said:
Getting a bit bored with all the naysayers on how sequential isn't worth doing.....
This is only the case if you don't change your injector spec from what it was on Batch fired, to get a gain in power your firstly need to reposition the injector somewhere along the inlet tract (ie no longer pointing at the back of the valve), Racing engines tend to have the injector just over the trumpet for this very reason.
Secondly you're trying to achieve open valve injection which usually means a much larger injector or fuel pressure to get it all in in time. This achieves a couple of benefits; one the tuning pulse is stronger due to the increased density of the charge (as its now cooler due to more fuel evaporation and the mass of the fuel along the entire inlet tract) Also you achieve control of the fuel timing in valve opening cycle which usually means you need overall less fuel injected (compared to batch fired) to achieve the correct in-cylinder mix and a more fuel efficent race car doesn't need to carry as much fuel and so is lighter etc.
The problems of achieving a power friendly sequential set-up are mainly that its not very nice to drive on part throttle (especially if your throttle is downstream of your injector) as the air-speed is too low and fuel drops out of the mix and forms puddles up down the port. And gets caught on your partly opened throttle etc.
In an ideal set-up you have 2 injector locations one conventional and one at the top of the port and you switch over at high throttle values.
It also helps emissions quite a bit but who cares about that...?
Matt
Eh? Who said it wasn't worth doing? I've read the entire thread and I can't see it. What I said was: I'm surprised that a 5L needs THAT much fuel.
As for caring about emissions: the way Numptyland is going, soon you'll be lucky to have an engine to care about, never mind its bloody emissions.
350matt said:
Getting a bit bored with all the naysayers on how sequential isn't worth doing.....
Interesting to hear the inside line.
It occurs to me that even if you get the injection timing right you won't get a uniform fuel distribution in the charge because the air speed is not uniform over time. A possible devious trick that occurs to me is to put downstream injectors pointing upstream, so that the 'distance' that the fuel carries upstream is more or less constant (determined by the fuel speed and drag characteristics) regardless of the air speed.
* by distance, I mean the amount of air that the fuel goes past before it stops. Not a simple measurement relative to the manifold.
Under part throttle conditions the throttle plate would contain the fuel, limiting the wetted area. Under wide throttle/low rev conditions it might be necessary to shape the manifold to constrain the fuel and prevent mega-stand-off (flame thrower).
Probably nonesense ...
Or we could have some kind of bernouille influenced device which administers fuel in direct proportion to the air speed .. that way each port is only fuelled when air is moving through it, and the fuel flow could then (say) be variable according to air speed, but as the flow would vary as the air speed squared you'd need to introduce some kind of air bleed arrangement into the fuel nozzle and a kind of mixing chamber (like an emulsion of fuel and air) between the two.
Bloody hell I think i'm onto something .. a sequential fuel delivery system that's air speed driven and neatly gets around the pressure reduction varying as air speed squared.
All I need now is a trendy racey name .. hmm .. something italian might do it
Bloody hell I think i'm onto something .. a sequential fuel delivery system that's air speed driven and neatly gets around the pressure reduction varying as air speed squared.
All I need now is a trendy racey name .. hmm .. something italian might do it
trackcar said:
Or we could have some kind of bernouille influenced device which administers fuel in direct proportion to the air speed .. that way each port is only fuelled when air is moving through it, and the fuel flow could then (say) be variable according to air speed, but as the flow would vary as the air speed squared you'd need to introduce some kind of air bleed arrangement into the fuel nozzle and a kind of mixing chamber (like an emulsion of fuel and air) between the two.
Bloody hell I think i'm onto something .. a sequential fuel delivery system that's air speed driven and neatly gets around the pressure reduction varying as air speed squared.
All I need now is a trendy racey name .. hmm .. something italian might do it
You know you could be on to something there! That would be SUper!
Matt,
I must confess I feel sequential is one of those things people use to boast about down the pub rather than being of any use or have any real time gains. In a 4 cylinder engine the valve is open for around 30% of the time, so to inject the required fuel within that time period would be quite a feat, especially when you concider at 6000rpm you have 10mSec between one complete cycle, so 30% of that would be pretty damn small! If you could acheive it with huge injectors then your idle pulse width would be so small it wouldnt be possible to control. Im not saying I wouldnt go for it when we get it in MS, but Im far from being convinced its worth spending any money on it,
Phil
I must confess I feel sequential is one of those things people use to boast about down the pub rather than being of any use or have any real time gains. In a 4 cylinder engine the valve is open for around 30% of the time, so to inject the required fuel within that time period would be quite a feat, especially when you concider at 6000rpm you have 10mSec between one complete cycle, so 30% of that would be pretty damn small! If you could acheive it with huge injectors then your idle pulse width would be so small it wouldnt be possible to control. Im not saying I wouldnt go for it when we get it in MS, but Im far from being convinced its worth spending any money on it,
Phil
Well just to give you some numbers on the F1 engine it was worth around 70-80Bhp to get the injection timing map right, and this was with pressures of 25Bar and injection durations of around 2.5msec at 18,000rpm.
Now if you scale this back a bit to real world figures say 6000Rpm with a 90% volumetric efficiency and a 270° cam then you'd need about 7.4msec injection time. I know of one 2ltr 4 cyl touring car engine that a mate is working on which picked up about 17-20Bhp by applying this sort of injector spec.
You're quite right about struggling to control the big injectors at idle but that's why I suggested the two injector set-up, altenatives are variable fuel pressure regulators or reverting to batch injection at lower engine loads.
Matt
Now if you scale this back a bit to real world figures say 6000Rpm with a 90% volumetric efficiency and a 270° cam then you'd need about 7.4msec injection time. I know of one 2ltr 4 cyl touring car engine that a mate is working on which picked up about 17-20Bhp by applying this sort of injector spec.
You're quite right about struggling to control the big injectors at idle but that's why I suggested the two injector set-up, altenatives are variable fuel pressure regulators or reverting to batch injection at lower engine loads.
Matt
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