volumex

[junior]

What are the pro's and cons of the volumex?
How would the vortech compare?
http://www.vortechsuperchargers.com/welcome/index.asp
Has anybody used one?

[Wallace]

IMHO - as Will would say . . . .

Right - the one big advantage of the Volumex is that all the pulleys, manifold, mounts etc etc come with the engine. You buy any aftermarket blower, it's a lot of time in the machine shop making up mounts, manifolds etc etc.

A more modern design with say integral compression such as a sprintex etc would be more effecient - and therefore "better". The volumex manifold is known to be crap as well - limits it to about 180 bhp (according to Guy Croft who tunes twin cam engines for a living). So potentially, a different blower with a better design of manifold could give a lot more boost with less temperature rise of the inlet charge (potential to fit an interccoler ??)

When all's said and done - the Volumex is a fairly crude 2 bladed roots type blower - there's nothing fancy about it - it has no special advantage over any other. There has been some talk about just because it was developed by Lancia, Abarth, whoever, it somehow is "better" than anyother. Personally, I can't see how - the laws of physics still apply whoever designed it ! I't's ok for about 8-10 psi boost, then it's effeciency falls like a stone - just like anyother roots blower.

IMHO - of course !!

[A1.6HPE]

Hello Junior,
According to that web link the Vortech is the best thing ever. I didn't find anything that describes what they really offer, but it seems to me to be a gear/belt driven turbine. It is like the output half of a turbocharger, driven mechanically rather than by the exhaust gas pressure.
So the main difference between the Vortech and the Volumex is that the Vortech is a turbine and so performs best at very high speed whereas the Volumex system uses a compressor which performs best at lower speeds. Effectively it is like comparing a Turbocharged engine against a Supercharged engine. The Volumex system is more about providing usable power and torque whereas a Turbocharger arrangement tends to be more about getting maximum power and torque and that generally results in an engine that needs to be revved hard to get the effect. The comparison is like the difference between a high revving low capacity engine and big lazy V8. The choice depends on your driving style, Volumexes are for drivers that like decent performance but don't want to be red-lining the revs every time.

[Pope1]

Junior, welcome to the forum. How's Worksop? Haven't seen that town since I was at Welbeck more than 25 years ago 8O .

I've also wondered whether it might be possible to fit a different supercharger to a VX engine and improve performance and that dreadful fuel economy. I GUESS it might be possible to engineer the Vortech unit with suitable gearing to match the VX's style of power delivery, change the manifold design and go over to fuel injection at the same time. However, I already know that I couldn't afford to even think what that might cost let alone do it as i don't have the skills (or the time) to engineer it myself. Much easier to convert the VX into a turbo or just start with an Integrale or Thema turbo engine instead unless you know what you're doing or have access to facilites at a reasonable price. You won't get a VX-style powerplant but it would be easier to do. :D

[SubGothius]

:idea: I have to wonder if anyone's ever tried retrofitting a VW G-lader type of supercharger (e.g. as used on the Corrado G60 before their VR6 engines came out) to our Lampredi DOHC-4, and if so, what the performance characteristics would be like...? Mebbe Guy Croft could pay a visit to G-Werks (http://www.G-Werks.com/) at the south coast and see what they might cook up together... :D

Other Supe options/types described here (http://www.sportcompactcarweb.com/tech/0107scc_garage/) -- hm, given the shape of Lancia's shield logo, a Wankel rotary compressor seems tempting, but one would prolly hafta fab one from scratch (not inconceivable in this era of precision CNC billet machining...)!

[omicron]

There are quite a lot of cheap Mini Cooper S superchargers about as many owners upgrade to the Works package which replaces the supercharger.

The old supercharger which generally only has been used for a few months (if that) is often sold on Ebay.

Andrew

[Tom McGaffigan]

Not sure I agree with all the posts about the Volumex supercharger being a lump. The Volumex with it steel rotors is able to run very tight rotor to rotor and rotor to case clearances resulting in high volumetric and adiabatic efficiencies. Typical clearances for ohther superchargers with aluminum rotors is .012 to .014 inches. A Volumex runs .004 inch clearance. Guy Croft in his Tuning and Workshop book states that he built a 215 hp Volumex for a Stratos kit car. There are photos of the car and engine in the book. Roots type superchargers have vastly superior low RPM boost response when compared with a Vortex centrifugal type. A Vortex has to spool up just like a turbo. Granted the adiabatic efficiency of a high boost turbo is better than a high boost roots type like a Volumex. In 1983 Lancia claimed 70% adiabatic efficiency for the Volumex at 6.5 PSI of boost. As for gas mileage I get can get 25 MPG (the small US gallons not the big UK gallons)at 80 MPG. My VX has higher compression than the original VX thus that helps and I do have the tall VX transaxle. But to take away from the MPG, I also have very hot cams and an overdrive pulley kit installed. It works for me, over 200 hp and 25 MPG at 80 MPH and its very reliable! I have put a combined 200,000 miles on the 2 Volumex that I installed in my Scorpion Montecarlo. Instant boost even at idle, just open the throttle.
Tom McGaffiagn
2 liter Volumex in a Scorpion Montecarlo :twisted:

[Will]

OK,
Well, I'll have to agree with Tom (to a point, anyway) on this one.
The volumex is not a BAD unit, but there are better designs available today. There are better engine designs too, for that matter.
The advantage of a blower like the Vortech, etc. is that is is not that hard to plumb to the engine. It's a pressure-pipe blow-thru type setup like a turbo. The centrifugal units tend to behave a little bit more like a turbo, less in the low end and higher output into the high end of the rev band.
A small, super high efficiency unit like the Powerdyne, which uses a planetary gear drive, would probably be the best unit to mate to a TC.
As far as 180bhp being the limit for a SC(cough cough) don't think so.
It's easy to look at the Vx manifold and think it must be horrribly imbalanced, BUT bear in mind two important things:
a) The thing does not flow like on a flowbench, since the valves open in sequence, and
b) The ports that draw a little more air (1,2) get proportionally even more fuel (since fuel has higher mass and doesn't follow the bends as well as air does) which helps hedge detonation in those holes.
Of course, unless you build the snot out of the motor first and/or use an overdrive on the vx, you'll find it may not be that EASY to get over 180BHP out of the motor, but it is certainly possible.
Also, a 180BHP vx motor is a lot nicer than a 180HP N/A motor due to the torque increase. You can get 200HP out of a N/A motor, but you'll have to wind the poor thing so high that the only time you'll SEE the 200HP is on the dyno, if you follow the logic in that statement ;).
The VW G-Lader (40 or 60 I think) mentioned earlier has a history of being total shite, FYI. They average something like 35-40K before self-destructing. Go over to a VW forum, those guys are always whining about them.
BTW- did somebody say Wankel earlier? I'll probably get ostracized for this, but I've always thought a blown Cosmo 3-rotor (B-20) would be just awesome in a Monte/Scorp. That'd be about 400HP in full pro street trim, so would probably be best in N-S configuration with a Porsche/VW or Hewland type box.
WHEEEEEEEE!

[SubGothius]

BTW- did somebody say Wankel earlier? I'll probably get ostracized for this, but I've always thought a blown Cosmo 3-rotor (B-20) would be just awesome in a Monte/Scorp. That'd be about 400HP in full pro street trim, so would probably be best in N-S configuration with a Porsche/VW or Hewland type box.
WHEEEEEEEE!I did say Wankel, albeit in the context of a rotary-configuration supercharger (the Wankel design was originally intended as a blower device, before they realized it'd also make a nice engine on its own 8) ); that said, I agree that the Mazda 20B engines (2.0L 3-rotor derived from the 1.3L 13B engine used in later RX7s) are niiiiice... Gotta wonder how even a more recent Renesis design from the new RX8 might fare in a Scorp/Monte (properly tuned and blown, natch ;) )...

[SubGothius]

[deleted duplicate post -- forum acting up again... :roll: ]

[chrisc]

It's easy to look at the Vx manifold and think it must be horrribly imbalanced, BUT bear in mind two important things:
a) The thing does not flow like on a flowbench, since the valves open in sequence, and
b) The ports that draw a little more air (1,2) get proportionally even more fuel (since fuel has higher mass and doesn't follow the bends as well as air does) which helps hedge detonation in those holes.


The guys who bought the engine out of my old 84 vx did so because they had destroyed an engine through detonation in 1 & 2, because they were running a modern mercedes blower and were using the stock manifold. They reported that they had done muchos playing trying to get an even mixture but found that 3 & 4 fouled or that 1 & 2 ran lean..

Unfortunately I dont know anything more than that!

[Wallace]

Amazing ! I was expecting a really good rant from Will - and didn't really get one !!!!!!!!!! :lol:

I'll look in Crofts book - I'm sure he says 180 is the max somewhere . .

But it IS a bad design - look at virtually any modern design (blown or not) and you'll find a nice big plenum chamber with equal length runners comming off it . . unlike the cast ally tree branch the VX uses ! And I know the torque figure is better etc etc but I've always wondered how the vx engine only produces about 15 bhp peak over standard - with LARGER inlet valves . . .. .

The vx blower isn't pants exactly - but the execution of it isn't as good as it could be and a more modern type with internal compression such as a sprintex will "be better" in terms of effecincy. A different set-up will also allow a chargecooler to be fitted which is always a good thing with lotsa boost. All books I've read about roots type blowers state that the effeciency drops to below 50% at anything in excess of about 10 psi boost - depending on design.

[Tom McGaffigan]

Wallace,
I would agree the Volumex intake manifold is not perfect but on the other hand it is not that bad. As far as a stock VX goes the reason the hp is only 135 is that it has a 7.5 to 1 compression ratio, lousy cams, lousy exhaust system and only 6.5 lbs of boost. The stock Volumex was designed for torque, not hp. Thats why it has 150 ft lbs of torque at less than 3,000 RPM. In 1983 there were no knock sensors, ignition retard or engine management systems so Lancia dropped the compression ratio to 7.5 to 1 so that even on really lousy gas there would not be any detonation. Today you can bump up the compression ratio, increase the supercharger drive ratio, add cams and header, install a good CD ignition, add a DCOE carb and enjoy a: flat torque curve, big HP and yes even good gas mileage if you drive reasonably. :twisted:
Tom McGaffigan

[Tom McGaffigan]

RE: Volumex horsepower
Oh yea, I think you will find in Crofts book, in the owners section, a reference to Peter Luxfords Stratos replica with a 215 HP Volumex. It has a stock manifold and a down draft carb. :twisted:
Tom McGaffigan

[omicron]

page 224

[Wallace]

Page 150, photo 12/7 .. . "it is impossible to get more than about 180bhp from standard manifold (whatever carburettor is used).

If Guy's around - could he tell us which one's right ? !!!!!!!!!

[Wallace]

Only what I read .. .

page 150, photo 12/7 . . " it is impossible to get more than about 180 from standard manifold"

Thoughts Guy ????

[Pope1]

Quite honestly, I've started wondering whether we're prehaps not expecting a little too much from our Volumexes, myself included. I have to say that Tom's experiences always give me cause for hope and the will to go on (spending money on that damn car) but I have started to question whether it's really worth it. For me the real question is what does one have to do to get around 200hp from a VX unit and HOW MUCH DOES IT COST?

[Wallace]

Lancia's/Fiat's are NEVER worth it - but that's not the point !!!!!!!!!!

I think someone somewhere did a version without a carb but with injectors welded onto the manifold - with seperate sensors in each exhaust runner, you could then try to optimize the mixture - and you wouldn't get perhaps the amount of problems with unequal distribution . . . . but it's a bit of welding and mapping to be done .

And an overdrive pulley would be necessary as well . . . . .

[Will]

Regarding Chris' comment on the MB blower installl, tha'ts EXACTLY what you should get if you are running bank-to-bank port injection!
Less air down 3 and 4, but same amount of fuel will make them rich, and one and two go lean.
The options as I see them are:
Carbs (works, but EFI works better)
True sequential injection w/individual injector trim (probably best)
TBI on B-2-B injection (the way I'll be going- has some upside and some downside elements)

The best way I know of to check A/F ratio over time is still to read the plugs, yes, I'm aware that you could mount four 02 sensors, but reading the plugs is the quick and easy way. A well-tuned stock Vx should have plugs that are virtually identical. This is made a little bit more complicated by the engine theoretically producing more heat in 1&2 holes- although I don't know specifically how much more. I can post pics of plugs numbered by hole, but the difference is so slight that it might not even show up in a pic.

The only reason I can see an MB blower setup behaving any differently than the stock roots unit is in the case of port injection (would create exactly what Chris described) or if the blower was one of the whipple type that feed from the end like the T-bird Supercoupe blower. I have no idea how the fuel comes out of there, but it doesn't take a whole lot of imagination to realize that if the mixture blew out at an angle, all of the fuel that was supposed to go to 1 and 2 could get slammed into the mani wall at #1 and puddle out. Again, purely conjecture because I don't know the MB blower configuration- but the Vx I do- and that delivers fuel pretty darn evenly all things considered.

-Will

[Pope1]

Yes, I'm very much with you on the point of cost-justification. I just feel that I should get some kind of buzz every time I drive the beast though. I always used to have a sense of occasion and anticipation when I drove it before. Instead it's starting to make me feel that, although the handling is a delight, it doesn't have enough grunt, is not smooth enough and is too noisy/unrefined considering the lack of grunt. I still live in hope that I can do a few relatively minor things to rectify the issues but I'm getting to the end of the list of possibilities fast. Oh yes, it does now have an overdrive pulley fitted, for what that's worth.

[andybeta]

Like any engine, modifications and improvements are genearally time consuming and expensive. If you measure the success of your investment on the basis of ££££ it gives back to you, you will for sure be disappointed. Significant hikes in output are not for the faint hearted and are definatley a labour of love. It also worth knowing before you start that the path you're following is the most efficient to reach your outcome.

The Beta engine is well over 20 years old and the supercharged engine is never going to produce shed loads of grunt. Isn't 200bhp and the equivalnet torque in a tuned engine enough??? By modern stds that is still pretty good......Even if alot more could be got I don't think the rest of the car even in good std spec could cope. I think a well built enigne producing around 200bhp is more than sufficient for the Beta VX. The std output was only 135bhp/150lbs torque that's a 50% increase, pretty good going really if indeed that's what you end up with. Also a tuned or lightened engine will be a whole lot more responsive so will feel so much more willing to be revved if that is your style. There are so many factors, the combination of which, if chosen carefully, can still produce a really good fast Beta. Why not try and reduce some of the Beta's weight if speed and acceleration are your ultimate goals if you can't increase the grunt?

[Wallace]

I'm afraid the old tin worm is pretty good at loosing weight on Lancias !

[Pope1]

Andy, I couldn't agree with you more and believe me if I had stopped to count the economic cost, I would have given up long ago.

Yes, indeed I would be very happy with 200HP but it doesn't feel anywhere close to that at the moment. Maybe I've been spoilt by the turbocharged cars I've owned since I last had my VX on the road or maybe there's something wrong with it that I have yet to find, but it isn't thrilling me like it used to.

It's difficult to see where I could save signifcant weight without compromising its abilities as a road car. It's also lighter than my bloated 200HP Golf which has quite tall gearing, so I'd expect the Beta to do as well with a wedge less power, but that's not the case so far. I have started wondering what it would be like with an IE gearbox and thought I might try driving around without using fifth to see whether I could live with a highing revving beast. In the meantime, I will check the valve clearances and do a compression test at the week-end to get an idea of its internal health.

I've not given up on it and I don't expect it to make sense, I'd just like it to be fun again. Then again, I guess quite a few guys in their forties say that about their wives too! :lol:

[Pope1]

By the way guys, I sent a personal invitation to Guy Croft and asked him to comment in this thread on the 180HP and standard manifold issue. He declined, so I guess we're on our own unless anyone is going to contract his services for a specific project. I've already been that route, so it must be someone else's turn. :lol: Sorry, I'm in a frivolous mood this evening.

[A1.6HPE]

Hello all,
I thought that the Volumex ethos was all about torque rather than power. The Volumex cars were (imho) aimed at enthusiastic drivers who didn't want to be revving the head off their engine but did want an engine that was tractable in the more civilized mid revs band - hence the green band on the tachometer.
I have an S3 Thema Turbo that produces 203 bhp in standard form but there is a noticeble difference to its character when in "hooligan mode". I think that the Volumex concept is "gentleman driver".
In terms of ultimate VX power, surely the Lancia Rally would be the example to follow with its engine architecture.

Leo

[Pope1]

I've been turning that over in my mind as well and it's one reason why I'm not wildly enthusiastic about going the shorter gear ratio route. At the moment my VX certainly doesn't feel like it would make a great screamer, in fact it feels more like a diesel. Pulls well between 2000 and 4000 with relatively little additional grunt beyond that point and that's with an IE inlet cam. Can't remember whether it was like that before. Does everyone else find the same thing?

[Pope1]

Tried running it with octane booster today as I remembered that's what I did before. It certainly runs better and is more willing. How do you guys in the US manage with 91/93 octane?

[A1.6HPE]

Hello Chris,
Who fitted the IE inlet cam - was it yourself or Guy Croft?

Leo

[Pope1]

It was Guy, and I feel that I should point out that when I first got the car back from him (10 years ago now) it was exactly what I had asked him for.

[andybeta]

Chris try some octane booster/additive. My preference was for superunleaded 96-98 octane mixed with Millers VSP (recommended by Hamish but unfortunately withdrawn in America due to some of the ingredients) the engine was transformed. I think this combination got near enough 99/100 octane as the Millers claimed to add 2 octane points, even with normal unleaded 94/95 octane + Millers there was a significant increase in performance.

I recognise where you're coming from with the Beta, but realistically you're being very hard on your VX judging it against more modern turbo engines - it will struggle. It's an old design. My std VX engine is no match for my remapped modern diesel kicking out 155bhp and 254lbs torque and doesn't seem half as smooth, but then again the diesel was built 4 years ago so has the advantage of a few more years of technology. It also does 50mpg whereas the Volumex does around 25-27mpg.

Try an additive. There are good reports of Redex if you can't find a Millers mix, but running on normal straight unleaded will leave the performance pretty lack lustre and it will pink and burn the valve seats.......

I wouldn't go for the IE box, not unless you're thinking of hill climbing, or sprints. The VX box is a much better proposition especially in a tuned VX engine. I would try cheaper and easier solutions first.

Good luck

[andybeta]

Chris try some octane booster/additive. My preference was for superunleaded 96-98 octane mixed with Millers VSP (recommended by Hamish but unfortunately withdrawn in America due to some of the ingredients) the engine was transformed. I think this combination got near enough 99/100 octane as the Millers claimed to add 2 octane points, even with normal unleaded 94/95 octane + Millers there was a significant increase in performance.

I recognise where you're coming from with the Beta, but realistically you're being very hard on your VX judging it against more modern turbo engines - it will struggle. It's an old design. My std VX engine is no match for my remapped modern diesel kicking out 155bhp and 254lbs torque and doesn't seem half as smooth, but then again the diesel was built 4 years ago so has the advantage of a few more years of technology. It also does 50mpg whereas the Volumex does around 25-27mpg.

Try an additive. There are good reports of Redex if you can't find a Millers mix, but running on normal straight unleaded will leave the performance pretty lack lustre and it will pink and burn the valve seats.......

I wouldn't go for the IE box, not unless you're thinking of hill climbing, or sprints. The VX box is a much better proposition especially in a tuned VX engine. I would try cheaper and easier solutions first.

Good luck

[Pope1]

Andy, thanks for the input. What a co-incidence! I did exactly that today and posted something earlier but due to the forum page issues you probably missed it.

You're right about it being unreasonable to expect the VX to compete with modern machinery and I've got over my initial disappointment after last week-end's VX trials. That said, I think that my main disappointment was that the car did not seem to run like before when I thought it ought to. I'm going to systematically check as much as I can during the next month and hope to bring about gradual improvements. For example, I took care of some vibrations today by getting rid of the engine stabiliser with nylon bushes that I have been trying and put back in the poly one. More of that another time.

BTW, my car used to do 14 mpg over here for a variety of reasons that I won't go into now. I'd be over the moon if I saw 22 mpg. That was one major running problem that I wanted to sort out and I have already good progress so far. Guy Croft did some mods (to the valve seats I believe) so that it could run on unleaded but I agree that the octane booster is still the way to go.

After a bit of a drive today I also decided that the IE gearbox was not such a good idea. The standard box seems to suit the character of the engine much better.

[Will]

Not to change the subject, but the cheapest way to add torque is nitrous. You can do it on a bone stock motor and get a great power curve 60-120MPH , but of course as the motor winds out, the nitrous falls off. You could do a 2-stage, but I haven't tried that. Just something to think about- definitely the best bang for the buck performance wise at about $450 total for the NX system, Zex, Venom , etc will run a few bucks more.
No problems related to the motor directly, except head gaskets- but back then, I could not find anything except stock Payen (NG for forced induction) or solid copper (leaked.) Have since developed some seal leaks- perhaps from extra blowby?

Anyway- back to the Volumex discussion;
I've probably posted this before, but (nearly) all the info I've got on the volumex and R10 superchargers is now collected here:

http://www.savetheledges.org/test/AVS/sc.html

Also note that the polished Vx that reads "sold to Tom McGaffigan" is NOT the one in his car- Tom already had his Vx car and bought this one either as a spare or for some top-secret project (what are you doing with that one, Tom?) I suspect he may be planning to build something even more demonic- look out for those Californians!

-Will

[andybeta]

Chris try some octane booster/additive. My preference was for superunleaded 96-98 octane mixed with Millers VSP (recommended by Hamish but unfortunately withdrawn in America due to some of the ingredients) the engine was transformed. I think this combination got near enough 99/100 octane as the Millers claimed to add 2 octane points, even with normal unleaded 94/95 octane + Millers there was a significant increase in performance.

I recognise where you're coming from with the Beta, but realistically you're being very hard on your VX judging it against more modern turbo engines - it will struggle. It's an old design. My std VX engine is no match for my remapped modern diesel kicking out 155bhp and 254lbs torque and doesn't seem half as smooth, but then again the diesel was built 4 years ago so has the advantage of a few more years of technology. It also does 50mpg whereas the Volumex does around 25-27mpg.

Try an additive. There are good reports of Redex if you can't find a Millers mix, but running on normal straight unleaded will leave the performance pretty lack lustre and it will pink and burn the valve seats.......

I wouldn't go for the IE box, not unless you're thinking of hill climbing, or sprints. The VX box is a much better proposition especially in a tuned VX engine. I would try cheaper and easier solutions first.

andy

[Will]

Chris, I think I know part 'o your problem- go check your post on timing!
-Will

[Tom McGaffigan]

In Guy Crofts book, Guy states
Page 150, photo 12/7 .. . "it is impossible to get more than about 180bhp from standard manifold (whatever carburettor is used).

Guy was refering to the carb to Volumex manifold not the Volumex to engine manifold. The carb manifold puts both carb throats (stock or DCNF) in line, almost is series, rather than in parallel. Put on a DCOE with the proper manifold to the supercharger and in excess of 200 hp is possible. You will need to: up the supercharger drive ratio, add cams, add compression, port the head, increase the valve sizes, add a big exhaust and add a better ignition system. BTDT
Tom McGaffigan
2 liter Volumex Scorpion / Montecarlo
:twisted:

[Guy Croft]

Tom - hi, "RE: Volumex horsepower
Oh yea, I think you will find in Crofts book, in the owners section, a reference to Peter Luxfords Stratos replica with a 215 HP Volumex. It has a stock manifold and a down draft carb"

Just for the record, Pete's is a sidedraft 45 DHLA on a GC manifold, not a downdraft, 32mm chokes. cc 2 liter. 44/36.5 race valves, fully flowed, Beta ie inlet Vx ex cam, 7.5/1 CR, 4-1 x 36" 2 in bore header, twin Porsche turbo mufflers.

GC Estimated bhp at time of build in June 92 was 190 bhp, rolling road test was at Torque Developments, their data was 170bhp at wheels, 215 at flywheel.

Regards,

Guy

[Will]

The Volumex downdraft manifold is a triple-whammy. Not only does it have two 90 degree bends of less than 1.5* pipe diameter, it has them stacked right on top of each other, in a what HVAC guys refer to as a "close double ell" configuration. That's worth an additional 15 percent of the sum of both ells in low-velocity, smooth walled house duct, who knows how much in the bumpy old Vx intake manifold? I'll bet you could make a smooth pipe wrap 270 degrees and come out ahead, or at least break even, but space is the issue- if you've got enough to make a 270, then you've probably got enough to mount sidedraft carbs. If you don't have any room for bulky DCOE's, you can use throttle bodies only and injection later in the pipe.
I've got a Buick 2.5 TBI that looks about right, my only concern is it's single injector, I'd like dual. It mounts in about the same physical space as a DCOE (a little less) but it also has one big bore instead of two little ones, which means lower velocity and should eliminate the need for any air horn type stuff.
Unfortunately, the 2-injector TBI's aka double barrel, are big enough in the throttle plate(s) that I'm concerned that the accellerator pedal will lose modulation and become more like an on-off switch, and cutting a nautilus-shaped cable sector is a PITA. So, still looking for the "right" TBI or side feed injectors so the TBI can become a TB only.