Turbo or supercharged Sevens

[Fun to Drive]

An appeal to you guys and gals on turbos in particular.

 

Do any of you have experiences of a Seven or other lightweight sportscar with a high power turbo?

 

I understand heat management is crucial, but I would like to know your driving opinions.

All opinions greatfully received.

 

Keep the revs up.

 

Mark

[Seven in SA]

Mark,

 

I would do a search on Turbo's in order to grasp as much info as possible.

 

To sum up the ones I have seen (no personal experience). A turbo is not suitable to the small lightweight seven, any lag will be detectable and spoil the driving experience. Imagine the turbo cutting in just as you are finalising the exit of a corner, you could say hello to your back end very quickly.

 

Superchargers I am not sure about but I think there was some issue over fitting them in under the bonnet of the seven. You might be ok with other lightweight sportscars depending on bonnnet height.

 

Max power is not everything, don't forget you have to transfer this to the tarmac. A turbo could easily spin your wheels in a light car. Weight is also crucial if you look at the R500 you have a responsive (bloody frightening I would imagine) engine that will rev up to 8500 with a predictable power feed. This will get you to 60 in 3.4 (factory figure) and if brave/stupid enought hit 150. Whilst this 'only' has 230bhp it will out blast almost everything. Then you look at some of the other 'famous' cars on blatchat, one being an R700 (not road legal yet). Having a normally aspirated engine producing 700bhp per tonne has to be near the ultimate. The turbo is used as a (relatively) cheap bolt on that can give more power but I susepct non of the driving pleasure of a normally aspirated engine.

 

Nic

 

Edited by - Seven in Sa on 13 Jun 2002 18:36:05

[murph7355]

Some Swiss nutters turbo'd their Vx's for something well in excess of 300bhp. Never actually met any of them to ask what they're like - I suspect most of them probably ended up in the scenery somewhere smile.gif So it's possible.

 

I've driven what I understand to be amongst the best turbo'd cars (TT, Saab, Impreza) and whilst there's a certain type of fun to be had, throttle response isn't high on the list in my opinion. Certainly not when compared to a well tuned nat.asp. engine.

 

For this reason alone I'd say turboing a 7 was a bad idea.

 

Superchargers on the other hand are something that would be interesting. Never driven one, but throttle response should be much cleaner owing to the way a Supercharger works.

 

TurboTechnics do a Supercharged Elise which is meant to be very good. I chatted with them when they first did this conversion about the possibility of dropping one in a 7. At the time they were too busy with Elise conversions to bother, but they may be up for it now?

 

Their installation is very compact and from the pictures I've seen I'm sure it would fit in a 7's engine bay. 270bhp is eminently possible I believe...and whilst not cheap to do properly, is almost certainly much cheaper than getting an engine builder to do you a nat.asp. engine.

 

 

[dino ferrana]

Apparently the Swiss Turbo VX's were very very fast. The problem with them was the lag or so I heard. Apparently you would be mid corner start oversteering lift off but the boost would run on and spin you! Terrifying if you ask me.

 

As for Superchargers I would love to know what one would be like. I imagine it would be nice to drive but the torque may overwhelm grip more often than not. Has anyone done one?

[Peter Carmichael]

Have TT managed to get a 270bhp engine to stay together for more than a week yet?

 

Peterid=teal>

253 BHP K-seriesteeth.gif, no gearboxbum.gifid=red>

[V7 SLR]

Turbos are the preserve of Fredy Kumschick (spelling?) the Swiss Caterham importer. Unfortunately I missed out on a visit to his place on last year's Se7ens List Euro2002 tour. Dammit. It looked like a very interesting visit from the pictures placed here. There are also diaries of the tour which may explain what was seen. thumbsup.gif

 

Anyway, the Turbo Technics Elise used a particular supercharger which is effectively a gear-driven turbo (there is a name for this charger, but it escapes me). This means that the boost increases with revs so you don't get the flat torque curve associated with conventional supercharges, however the supercharger itself is very compact and light and doesn't suffer from lag like a turbo. This particular installation in the TT Elise uses a special cast aluminium manifold to house 8 fuel injectors. This makes it very long so you wouldn't get it under the bonnet of a Caterham. You might get it under the bonnet of an SV but I think the angle that the K engine leans at would mean the manifold would poke out of the top corner of the bonnet rather than the side. Ugly..!! sad.gif

 

You could, I suppose, try to perform a similar installation to the TT one (engine internals etc) but using standard throttle bodies and your own home-brewed plenum (needs to be air tight to withstand the pressure of the charger). I don't suppose this is very hard, but I don't know what air pressures we are talking about. The TT Elise uses an Emerald ECU which is pretty easy to source, although EVO mag weren't very complimentary about the mapping. I find this odd as all other Emerald installations seem to be distinguished by the fact that their maps are so good.

 

A chap in Bromsgrove, Stu Boffy, has an Elise which he has built himself (with help, naturally) using a more conventional supercharger. I saw Stu's torque curve on the Emerald rolling road and it was at max torque from about 3000rpm and flat all the way to max rpm. His top end power was limited on that particular chart because he had some issues with bad running or misfiring at the time which limited his max revs, but the promise is definitely there.

 

I've got a pretty powerful NA K (not quite as powerful as Peter's or an R500), which I love, but the feeling of "Star Trek urge" you get with forced induction is very appealing. If I find the money one day, I'd like to try a supercharged Se7en.

 

I have a friend with a Cosworth Turbo Striker. Now this may sound a tad unbalanced (very light car with very heavy and powerful engine) but apparently it is an absolute hoot to drive. He has a little issue with the boost falling off early but he still makes some 240ftlb of torque. You might not want to race something like that around a tight track, but on a more open circuit I wouldn't like to bet that a NA Se7en could outrun him.

 

There was also a chap on the Se7ens list who unfortunately recently pranged his turbocharged Westfield. Until then he was running something like 330bhp and claimed that there wasn't much that could touch him on the straights. Although corners require a balanced car, they are also about how good a driver you are. With 330bhp you can mask your inability to take corners quickly with ludicrous acceleration and top speed. Maybe not much of a race car, but a fun track day tool nonetheless.

 

Most people here would disagree with forced induction and in general I have to agree with them, BUT it is a seriously fun carrot to dangle in front of anyone's face and I am tempted in the future... just in the interests of science and discovery you understand. cool.gif.

 

Edited by - V7 SLR on 14 Jun 2002 12:33:06

[Laurence Wilson]

If you are interested there is a review of an Exige with such an installation in this months EVO. They reckon it's rather tasty!

 

Cheers! teeth.gifid=orange>

Laurence 'LOZ' Wilsonid=purple>

[V7 SLR]

Mmm, I think it was the Exige to which I was referring inaccurately as "Elise".

[edmandsd]

We're still waiting to see the unveiling of the Quaife supercharged 2 lt BD Caterham with an easily obtained 350bhp and similar levels of torque. On paper it should be virtually unassailable in a straight line with circa 700 bhp per ton. I'd be concerned about how the chassis would cope with these levels of power and torque though.

 

If I had to choose between supercharged and turbocharged i'd have to pick supercharged every time so as to avoid the dreaded lag associated with turbos.

[Red SLR]

There is a turbo charged caterham around on the sprint circuit up north, cant recall any exact details but its fast!

 

 

 

X777CAT

[Dave H]

There was a turbo'd Se7en around down South a few years back - built by Steve Richie. Sierra Cosworth 2L with the smaller Escort turbo unit fitted. A claimed 290+ bhp, and a kick in the back like nothing I've ever experienced before. It weighed in at around 600Kgs, so power to weight was around 500 bhp/ton. The turbo lag wasn't too bad, provided you kept the revs up. I don't know what it was like on the track, but as a road car it was awsome.

 

Dave H

[DaveK]

Simon

 

The jpe turbo belongs to Bernard Hoggarth who sometimes posts on here IIRC he has just fitted a seq box to it as well.

 

Clive Kenrick built a Turbo 7 a few years ago. It produced 230 bhp at the wheels and was very fast with good road manners as it gave full boost at 1500 rpm, On road driving never needed dropping out of fifth gear due to the massive torque available (260 lb ft).

 

The fun aspect was missing as you didn't have to thrash the car to achieve illegal speeds whic i feel is part of owing a 7

 

Dave

[Fun to Drive]

Thanks for the replies.

Some of you have obviously looked into this in the past.

 

Have any of you heard of Sprintex superchargers? I vaguely recall lots of publicity in the 80's for Sprintex, claiming similar thermal efficiency to a supercharger but with the low lag advantage of a supercharger?

Are any of these units available?

 

Thanks again.

 

Mark

[V7 SLR]

There's nothing particularly innovative about the Sprintex, it's just a screw-type and I was amazed recently when investigating my dry sump scavenge pump how similar it is to a screw-type supercharger. The packaging of the Sprintex was it's strength. I believe they went bust or were bought up by someone else.

 

I was actually given a Sprintex in the late 80's, before I really knew much about engines. I used to go to a local garage where there was a chap who worked at weekends on "foreigners". He did a lot on my car in those days when I was getting by on about 60 quid a week working in an off-licence while still at college. He helped me to get a manifold cast to attach the Sprintex to my 1400 Mini's A-series engine. I think there were some seriously dubious engineering practices going on then, as I remember him telling me that he'd sent my con rods off to be "shortened". I still don't know whether he was joking when later I asked how they shorten them and he told me that they cut 2 or 3 mm out of them with a hacksaw and weld them back together. blush.gif

 

On the dyno of a Birmingham engineering firm we saw 136bhp which seemed enormous then and I was really looking forward to putting it back into the car but as we lowered it into the engine bay we realised for the first time that the twin SU's, which were mounted on top of the sprintex which itself was mounted above the rocker cover, would prevent me from actually seeing anything in front of the engine.

 

We removed the supercharging parts and I sold them for what I'd paid for them to a Midget owner in the area who was still using it successfully 8 years later (last time I saw him).

[John Reay]

They may have "shortened" the rods by offset drilling the small end. This is fairly common practice for lower the CR for modest boost applications and thus avoiding the expense of low compression pistons or the even more dubious route of double headgasket job.

 

I had offset drilled con-rods on my 8 injector 16v turbo Golf engine. This lowered the CR to 8.5:1 and I ran 11-12psi boost using a T25 turbo. Power and torque went from std 140bhp/125lbft to 215bhp and 220lbft torque.

 

Engine was very strong and robust.

 

John

[Mike Bey]

Check out this one for sale at Woodcote - 290bhp - £10,500!

 

Mike

[Morls]

Me, (you?)

 

I vaguely remember some hype in the car and bike press in the eighties for something that might be what you were thinking of...

 

IIRC it was a "Comprex", an unholy alliance of small supercharger, (for linear power & no lag), sharing either a manifold, shaft or impeller vanes with a conventional turbo, (for lag and flameswink.gif.

 

Either it wasn't as good as predicted, the governing bodies banned it or turbos got better...

 

My bet's on all three.

 

As for superchargers... Having driven a humble VW Polo with a such a device, (G40, Hello Coose thumbsup.gif), I think they're much nicer than the, admittedly old generation, turbo cars that I've driven.

 

If you didn't look under the bonnet you would just think it was a good 1800 NA engine, rather than the 1300 pushrod reality. No lag or bad temper just lots of torque...nice.

 

Mark