Individual Throttle Bodied TVR 5.0L with Megasquirt
Discussion
Hi there,
yeah, Im thinking of having another go at it but rather than using the Samco pipe simply get some more tube welded onto the main tube so it no longer will have the steps. Seperate lambda's is a good idea I hadnt thought of, but I got so fed up and just ripped it off and put the plenum back on so I could drive it
Phil
yeah, Im thinking of having another go at it but rather than using the Samco pipe simply get some more tube welded onto the main tube so it no longer will have the steps. Seperate lambda's is a good idea I hadnt thought of, but I got so fed up and just ripped it off and put the plenum back on so I could drive it
Phil
Might also help to switch to TPS as unless you fit a tapping with a manifold to multiple cylinders then your MAP sensor will be seeing a bit of fluctation of only reading off one cylinder.
Alternativly try a small damping orifice in front of the sensor about Ø1.0
Its possible that going sequential would also help as there tends to be less fuel sloshing around to cause problems
Matt
Alternativly try a small damping orifice in front of the sensor about Ø1.0
Its possible that going sequential would also help as there tends to be less fuel sloshing around to cause problems
Matt
I'd echo what matt says about MAP sensors drawing of single pipes, but you can get around any inbalance over indivdual inlets and the MAP issues by linking all the inlets together with a balance pipe arrangement .. just big enough to bleed the pressure differentials out across the multiple inlets .. might be all you need to do is drill and tap all 8 inlets close to the head mating flange and link them all together then take your MAP sensor from that balancing pipework.
Would be a crying shame to give in when it looks so promising
Would be a crying shame to give in when it looks so promising
I think Bill Shurvinton has put his finger on the trouble, can't believe I over looked it to be honest 
but its the fact that the 2 centre cylinders of each bank are joined and they are drawing air in from both throttle plates so they will be weaker than the outer 2. Well we are hoping its the trouble any how, so the gap is being welded up this week and Im going to try again the weekend.
I did try Alpha_N but the trouble wasnt that I couldnt tune it, it was that I couldnt get it to tune if you see what I mean
The plan for this is to use MAP untill the pressure is slightly under atmospheric then it will switch over to Alpha, giving me a 24x12 map 
as map is the only real way of tuning for efficiency, and then I can use TPS when I put my foot down.
Sequential may be something that MS3 will address, but Im still not convinced, maybe I need to try it and see what it does for myself.
Phil
but its the fact that the 2 centre cylinders of each bank are joined and they are drawing air in from both throttle plates so they will be weaker than the outer 2. Well we are hoping its the trouble any how, so the gap is being welded up this week and Im going to try again the weekend. I did try Alpha_N but the trouble wasnt that I couldnt tune it, it was that I couldnt get it to tune if you see what I mean
The plan for this is to use MAP untill the pressure is slightly under atmospheric then it will switch over to Alpha, giving me a 24x12 map as map is the only real way of tuning for efficiency, and then I can use TPS when I put my foot down. Sequential may be something that MS3 will address, but Im still not convinced, maybe I need to try it and see what it does for myself.
Phil
Hi there,
as the gap between the centre 2 cylinders on each bank is really tight the tubes were welded together before they were joined to the base, as the welder wouldnt have been able to get in to there to weld wit hthem on the base. This meant that there was a very slight gap between the tubes and the very centre of the base, so whilst they were not leaking to atmosphere they could breath through each others throttle plate. I got the gap welded up internally and re-ground it all down, now it is running really well! Im half way through tuning now and it looks like its cured the problems, I have a very strong idle and its a lot easier to tune. just cant beleive I didnt think of it!!
Phil
as the gap between the centre 2 cylinders on each bank is really tight the tubes were welded together before they were joined to the base, as the welder wouldnt have been able to get in to there to weld wit hthem on the base. This meant that there was a very slight gap between the tubes and the very centre of the base, so whilst they were not leaking to atmosphere they could breath through each others throttle plate. I got the gap welded up internally and re-ground it all down, now it is running really well! Im half way through tuning now and it looks like its cured the problems, I have a very strong idle and its a lot easier to tune. just cant beleive I didnt think of it!!
Phil
daxtojeiro said:
Hi there,
as the gap between the centre 2 cylinders on each bank is really tight the tubes were welded together before they were joined to the base, as the welder wouldnt have been able to get in to there to weld wit hthem on the base. This meant that there was a very slight gap between the tubes and the very centre of the base, so whilst they were not leaking to atmosphere they could breath through each others throttle plate. I got the gap welded up internally and re-ground it all down, now it is running really well! Im half way through tuning now and it looks like its cured the problems, I have a very strong idle and its a lot easier to tune. just cant beleive I didnt think of it!!
Phil
Where's Homer when you need him : Doh..
Well done - glad you got it sorted
Hi there,
well Im still tuning it, but its going really well, Ive been using AutoTune in MT as the VE values are all over the place as the tuned length varies with throttle position. Im definetly going to have to swap from MAP to TPS as the throttle increases, as I run out of map around 20% throttle. So right now Im tuning the lower throttle positions of under atmosphere in the plenum. Then I will start doing the higher throttle positions. I could do it using TPS all the time, but I would like to have some economy from it, so MAP has to be retained for cruising, etc,
Phil
well Im still tuning it, but its going really well, Ive been using AutoTune in MT as the VE values are all over the place as the tuned length varies with throttle position. Im definetly going to have to swap from MAP to TPS as the throttle increases, as I run out of map around 20% throttle. So right now Im tuning the lower throttle positions of under atmosphere in the plenum. Then I will start doing the higher throttle positions. I could do it using TPS all the time, but I would like to have some economy from it, so MAP has to be retained for cruising, etc,
Phil
daxtojeiro said:
Hi there,
well Im still tuning it, but its going really well, Ive been using AutoTune in MT as the VE values are all over the place as the tuned length varies with throttle position. Im definetly going to have to swap from MAP to TPS as the throttle increases, as I run out of map around 20% throttle. So right now Im tuning the lower throttle positions of under atmosphere in the plenum. Then I will start doing the higher throttle positions. I could do it using TPS all the time, but I would like to have some economy from it, so MAP has to be retained for cruising, etc,
Phil
well Im still tuning it, but its going really well, Ive been using AutoTune in MT as the VE values are all over the place as the tuned length varies with throttle position. Im definetly going to have to swap from MAP to TPS as the throttle increases, as I run out of map around 20% throttle. So right now Im tuning the lower throttle positions of under atmosphere in the plenum. Then I will start doing the higher throttle positions. I could do it using TPS all the time, but I would like to have some economy from it, so MAP has to be retained for cruising, etc,
Phil
Phil,
Whats the latest? I am really interested in mirroring your conversion on my 5.3 over the winter.
Andy
I gave up 
I simply couldnt get them balanced and tuned at part throttle and overrun, especially overrun. I know of someone else doing it and they are struggling with it all too and have put it on hold till the winter. I was going to have another go but after driving Robs 5.5 with the triple act plenum and talking to Rob Im now convinced this is as good if not better than ITB's. So Im about to cut 2 plenums in half and have 2 throttle intakes, one either side. This is going to be sooo much easier to tune it is untrue, and it should look good too, I hope,
Phil
I simply couldnt get them balanced and tuned at part throttle and overrun, especially overrun. I know of someone else doing it and they are struggling with it all too and have put it on hold till the winter. I was going to have another go but after driving Robs 5.5 with the triple act plenum and talking to Rob Im now convinced this is as good if not better than ITB's. So Im about to cut 2 plenums in half and have 2 throttle intakes, one either side. This is going to be sooo much easier to tune it is untrue, and it should look good too, I hope, Phil
plenums are good until you start putting wilder and wilder cams in usually. I know some people claim that the RV8 runs well on plenums and wild cams, but conventional wisdom doesn't support this on other cars. There's still a place for TBs on RV8s so stick with it Phil, there's a market out there 
The problem that TBs solve is flow reversion at low rpm low throttle openings if you have a lary cam. And from what you're saying the problem that they introduce is balancing all those throttle bodies? Presumably it's possible in principle, because people do use TBs on production cars. If the problem is sensitivity to small differences in throttle position at very low throttle openings, would it be possible to reduce the effect by having a seperate bypass through or round the throttle plate? This could be accurately machined and hence ensure that all cylinders get the same minimum flow under very low flow conditions.
trackcar said:
plenums are good until you start putting wilder and wilder cams in usually. I know some people claim that the RV8 runs well on plenums and wild cams, but conventional wisdom doesn't support this on other cars. There's still a place for TBs on RV8s so stick with it Phil, there's a market out there
Yep exactly my experience. With a triple throttle body plenum and a 248 cam I had to idle at around 1200 as it was so lumpy. After John Eales fitted the 8 TBs, it would idle at 450 rpm and was as smooth as anything.
GreenV8S said:
The problem that TBs solve is flow reversion at low rpm low throttle openings if you have a lary cam. And from what you're saying the problem that they introduce is balancing all those throttle bodies? Presumably it's possible in principle, because people do use TBs on production cars. If the problem is sensitivity to small differences in throttle position at very low throttle openings, would it be possible to reduce the effect by having a seperate bypass through or round the throttle plate? This could be accurately machined and hence ensure that all cylinders get the same minimum flow under very low flow conditions.
yup the throttle plates act as waveform interrupters in the best place possible, the individual inlet tracts. On most lairy cam engines you can gain useful low/mid range hp by running with the throttle partially closed so what you then need is some kind of fly-by-wire control over it to maximise the interrupter effect across the whole rev range where reversion is a problem.
If any electronics gurus are interested on working on this let me know!
All we need is for Phil to write the code for a the megasquirt to control it hehetrackcar said:
GreenV8S said:
If the problem is sensitivity to small differences in throttle position at very low throttle openings, would it be possible to reduce the effect by having a seperate bypass through or round the throttle plate? This could be accurately machined and hence ensure that all cylinders get the same minimum flow under very low flow conditions.
yup the throttle plates act as waveform interrupters in the best place possible, the individual inlet tracts. On most lairy cam engines you can gain useful low/mid range hp by running with the throttle partially closed so what you then need is some kind of fly-by-wire control over it to maximise the interrupter effect across the whole rev range where reversion is a problem.
If any electronics gurus are interested on working on this let me know!
All we need is for Phil to write the code for a the megasquirt to control it heheWhat effect would it have if you repositioned the injectors back to where they were on the standard manifold (near the flange that mates to the head) and blanked off the openings in the throttle bodies then link all the manifold ports together with a decent dia pipe to smooth out the induction pulses.
I guess this balance pipe would be more effective at small thottle openings, where you want it and be pretty much redundant at wide throttle opening. Could almost be considered as a mini plenum.
There you go, chew that over
Andy
else said:
trackcar said:
GreenV8S said:
If the problem is sensitivity to small differences in throttle position at very low throttle openings, would it be possible to reduce the effect by having a seperate bypass through or round the throttle plate? This could be accurately machined and hence ensure that all cylinders get the same minimum flow under very low flow conditions.
yup the throttle plates act as waveform interrupters in the best place possible, the individual inlet tracts. On most lairy cam engines you can gain useful low/mid range hp by running with the throttle partially closed so what you then need is some kind of fly-by-wire control over it to maximise the interrupter effect across the whole rev range where reversion is a problem.
If any electronics gurus are interested on working on this let me know!
All we need is for Phil to write the code for a the megasquirt to control it heheWhat effect would it have if you repositioned the injectors back to where they were on the standard manifold (near the flange that mates to the head) and blanked off the openings in the throttle bodies then link all the manifold ports together with a decent dia pipe to smooth out the induction pulses.
I guess this balance pipe would be more effective at small thottle openings, where you want it and be pretty much redundant at wide throttle opening. Could almost be considered as a mini plenum.
There you go, chew that over
Andy
If you link them they must all have the same size/length tube between all 8 of them and thats impossible as the other 4 are further away from the centre 4. Other wise they will all draw different amounts of air in as they can suck through from more than 1 inlet butterfly. I would think this would also be a complete nightmare to balance. I have to say I think that the twin intake plenum could be a better answer,
Phil
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