Volumex Injection ?

[TS131Volumex]

Hello there ,
Please advise an eager to learn novice ;
I am thinking of fitting an injection system to my Volumex supercharger for space-gain reasons .
1) A short Throttle body with a short trumpet/rampipe and sock should be that bit shorter than a dcoe with trumpet giving me more wheel clearence ?
2) A throttle body could be fitted with an upward incline again helping with wheel clearence ?
3) I would not need a cam run distributor , this time giving me better hood clearence ?
4) I would have the advantage of more efficient running from the programable ecu ?

Allthough it has not progressed as I hoped it would , I am very happy to have my car back with me now and I shall soon post an update with pictures of that which has been made since last posting and no doubt plenty of questions about other future plans .
Thank you . Matt .

[Testament]

I take it this is a beta VX motor installed in a Fiat 131? This is the same setup that I will be running in my car - from my measurements it's not feasible to run a DCOE, I was investigating using an IDF but I am leaning towards running injection also. If running injection an elbow could be fabricated to go on the supercharger intake and then mount a throttle body facing forwards.

I don't think a cam mounted distributor is a problem in a 131 - some models of 131 had this as factory fitment. Worse case it may foul a strut tower brace if running one. You cannot run the block mounted distributor with the supercharged engine though as the supercharger and its mounting bracket are in the way.

The issue is that the VX engine has a different ignition curve - you can't run any cam mount distributor without having the ignition curve reset to VX specs (or otherwise tuned) - you will run into detonation problems otherwise. If you are going to run injection, running distributorless ignition is probably a good idea.

I think injection may be a good benefit on the VX engine - to get a carb to run well seems to require quite small venturis which must cause some restriction and therefore restrict power to some degree.

[Guy Croft]

Good post.

I have no single copy of an OE curve for the Vx (and never saw one) but have looked at the Vx adv characteristic with a strobe numerous times and deduced (to my suprise) it to be the same as a normally aspirated motor, 10 deg static and 35 deg total at 5500. But - having worked in the past with an old 'MicroDynamics' piggy-back boost retard system on an engine running exactly 15psi gauge boost and found that only 8 degrees retard was needed from peak torque upwards and given the very low boost of the Vx on the 2 liter that did not surprise me at all. I am quite prepared to accept I may be wrong about the curve so if anyone has an actual factory curve could they please comment. Please do not scan OE data - it's copyright.


As for injecting I would definitely want to do 'inboard' ie: into the inlet manifold and not outboard of the blower intake. The danger if injecting outboard is the effect of the reverse pressure waves formthe rotors and the appalling mixture distribution in the 'log' manifold that is responsible for the power poor from that engine. Hardly worth fitting inj if you don't enhance the layout, might as well use a carb and save yourself a fortune in time and cost. There is at least one vehicle (trial car) on this side somewhere with that setup but I cannot remember where.

GC

[Testament]

I had heard of the distributor swap being a problem on a 124 running a VX engine with a 124BC ex. cambox distributor, but Now that I look it up it's looks like I'm probably wrong, the VX supplement says

static advance: 10 deg.
centrifugal advance at 3100rpm: 25 deg +/- 2 deg
max vacuum correction on engine 15 deg +/- 2 deg

Comparing this to the factory 131R map, the VX advance comes in more quickly but about the same amount as you say. (131 map shows 24 deg @5500rpm) unless the vacuum advance acts as a boost retard? It doesn't say anything else about it really, although it does imply the distributor is the same or similar to the Beta 2000 i.e. engine

As for injecting I would definitely want to do 'inboard' ie: into the inlet manifold and not outboard of the blower intake. The danger if injecting outboard is the effect of the reverse pressure waves formthe rotors and the appalling mixture distribution in the 'log' manifold that is responsible for the power poor from that engine. Hardly worth fitting inj if you don't enhance the layout, might as well use a carb and save yourself a fortune in time and cost. There is at least one vehicle (trial car) on this side somewhere with that setup but I cannot remember where.

Do you think if injection was added to the factory "log" thus removing the fuel distribution issue things would be much improved - or are you meaning that the whole airflow discrepancy in the log is so bad that it's not worth fitting injection bosses to it?

[Guy Croft]

Thanks!

The vacuum unit controls only the baseplate and is a contemporary vacuum advance. The advance peaking earlier - probably due to the need for spark earlier in the compression stroke to ensure good burn. The 124CSA peaked at 3800, presumably for the same reason. In setiing-up I've concluded that supercharged engines are less sensitive to advance than n/a ones, though I don't real data to back this up 'assertion'!

With injection into port via the inboard manifold (4 inj) you can direct the gasoline precisely where it_needs_to_go and maybe even tune the injectors individually (?) to the apparently rather chaotic airflow distribution in there. I say apparently for 2 reasons. Airflow tests using an 'air mover' at low pressure blowing thru inboard manifold as it would be on-engine show a very marked bais of flow to the front port. On engine it might be a alsightly different story ie: although the rear cylinders would get less than the front it might not be quite as bad as it looks on bare test because there will be a general overpressure in the manifold because only one cylinder is on intake at any time. Wear patterns on rings on carburetted & well-used units tend to bear this out, with the worst wear being at the rear due 'to much gasoline' and 'not enough air'.

G

[TS131Volumex]

Thank you Guy and Testament ,
It seems there might be a good deal more to consider and ' pay for ' than I and perhaps you Testament had thought . But something to consider if a decent alternative solution does not appear .
For reference my volumex is the one fitted to a Triumph Spitfire . It seems we should have overcome the dry sump pump fouling suspension problem but there is an issue with 'dcoe route' fouling wheel space and the distributor will definatley need a bulge in the bonnet ( allthough 180 deg turn will help ) , infact even the cam belt fits exactly against the existing gt6 bonnet bulge so a slight 1.5cm bulge/scoop might be needed there .
Luckily yesterday I came across a man called Tony Bianchi in a lock up 150 meters from my house . I thought had moved 15 or so years ago so was suprised to see him beavering away , converting a golf buggy into a scaled down Porche Gt3? paddock run around for some race team . He was a very prominent Porche engineer but gave it all up about 15 years ago to become a closet glass fibre / carbon fibre fabricator . His work is outstanding , including various very complex but beautifully engineered and finnished Porche rear wing designs all produced in a couple of very ' worked in ' double garages . He has Kindly agreed to come round on monday evening to advise me on moding/preping my bonnet , so could be one issue on the right track .
I shall take some updated pics tonight to illustrate .

[TS131Volumex]

induction/wheel clearence .

SPITVX 013 (640 x 480) (320 x 240).jpg (72.29 KiB) Viewed 8596 times

and again .

SPITVX 014 (640 x 480) (320 x 240).jpg (73.62 KiB) Viewed 8598 times

distributor/bonnet clearence .

SPITVX 016 (640 x 480) (320 x 240).jpg (67.21 KiB) Viewed 8595 times

old engine mount/susp' turret chopped to fit d.s.p .

SPITVX 006 (640 x 480) (320 x 240).jpg (71.79 KiB) Viewed 8598 times

old spitfire swing spring rear susp' .

Spit 131 on route . 013 (400 x 300) (200 x 150).jpg (55.54 KiB) Viewed 8595 times

new GT6 CV/coil over rear susp' .

SPITVX 002 (640 x 480) (320 x 240).jpg (60.21 KiB) Viewed 8598 times

bonnet off .

SPITVX 005 (640 x 480) (320 x 240).jpg (70.62 KiB) Viewed 8596 times

and on .

SPITVX 004 (640 x 480) (320 x 240).jpg (57.58 KiB) Viewed 8600 times

rear showing fuel tanks etc .

SPITVX 001 (480 x 640) (240 x 320).jpg (67.9 KiB) Viewed 8597 times

cam belt tight to existing bulge .

SPITVX 012 (640 x 480) (320 x 240).jpg (61.32 KiB) Viewed 8599 times

[TS131Volumex]

Seems Volumex injection has not put dglitten off ( see readers cars ) . VERY impressive , perhaps he should think about producing conversion kits ------------ wishfull thinking !

[Testament]

Would it be worthwhile to do a test of manifold flow to each port (blocking off the others as if their valves were shut) - the fuel does not like making all the bends etc. to get to #4 cylinder, and while the log design may not be ideal, the actual air flow difference between the four cylinders may not be so great?

[volumetrico]

Hi Matt,
I am sure I have seen the VX head-to-blower manifold modified to hold 1 injector per cylinder. I believe you will need to weld enough material to the manifold to allow for a seat to be machined to place the injector through. You'll also need to fashion something to bolt the fuel rail and injectors into place securely.

If you do still want to consider a throttle body and space is at a premium, I know Jenvey do a DCOE flanged throttle body that is only 30mm deep !

Not sure to what extent (if any) the rotors rely on fuel to cool them?

Regards,
Melo

[Guy Croft]

From a thermodynamic perspective it is much more efficient to inject downstream of the blower after the work has been done on the air (ie: compression) in other words inject into the inboard manifold.

Gc

[tmvolumex]

I believe David Beale installed fuel injectors directly onto his blower to head, Volumex, intake manifold. And yes, he had to weld on additional material in order to create a large enough boss for the injector.
Tom

[Guy Croft]

Yes, he did one on his own and then I did a new one for him.

I will publish a photo later..

G

[volumetrico]

Look forward to the photo Guy...I think I may have a photo at home, if its any different I will also post up.
I appreciate an injector firing into each port is the way to go for better fuel control/ atomisation etc.
Is it your view that the cooling and compression in the blower will not suffer as a result of pumping air only?

Thanks
Melo

[Guy Croft]

It's an immutable fact that compression involves temperature rise. Compressing the gasaoline with the air as I indicated above is thermodynamically less efficient than injecting after the air is compressed...

The operating temperature of the blower is well within safe limits and remember that although compression produces heat the rotors are constantly be cooled by incoming air. Provided that air is fed from a cool ie: ambient source of course..

You can only cool the charge (beyond the temperature drop induced in the manifold by latent heat of vaporisation of the fuel) by inputting more energy from a separate cooling system (or losing it eg: intercooler) and given the relatively low temperature rise induced in the air by the Vx blower (compared with the temperature rise caused by turbochargers operating at much higher boost - eg: 15psi plus) it is just not worth wasting time over.

GC