Anyone used forced induction on a Twin Cam

[bcmc33]

ARP make studs - just ordered a set to try - but getting the head off may be an issue as the studs will have to come out due to the chain guide in the front cover

Rohan,

ARP studs have allen key holes on the top for you to screw them in.
With the engine in the car you can't have the studs in place to drop the head on. I simply placed the head on the bock/gasket and screwed the studs in exactly as you would with bolts.

[rgh0]

Thanks Brian I assumed they must have some arrangement like that - screwing in would be relatively easy even without a allen key socket but getting out after a few years in the block could be a lot harder without a secure way of turning

The DHL shipment of bits from Burtons includng the ARB studs arrived today but i was out so i will get them monday. Just a little more work on the combustion chambers and I will be ready to assemble my new race engine.

cheers
Rohan

[seaandmoor]

Hi Burgundyben,
I haven't double checked on my laptop but I'm certain that I've seen provision for knock sensing on my MS version 2.3

[john.p.clegg]

Will the megasquirt EFI accept a knock sensor input?

I'd been keen to have a knock sensor in place to ease back on the ignition advance if it senses knock, it might prevent an unfortunate engine disaster!

Ben

Yes,I've got one on mine,retards the ignition with knock.

John

[Tahoe]

Interesting thread that skipped 3 years. I have given serious thought to a turbo on my car. I have turboed several cars and would go the route of a ball bearing water cooled CHRA. A properly sized turbo with charge cooler and limited boost. I wouldn't be looking for a mega HP machine, but a fun and responsive street car. It can be done without worry of a catastrophic event in the engine if designed properly. I did a crossflow 1600 once back in the early 80's without any issues. It was very low boost and didn't benefit from modern turbo technology and admittedly had too much lag, but worked fine Lag is not an issue today, and a proper air or water cooled charge cooler will keep things real. Probably won't go down that path right now, but I might just change my mind after the SEMA show. There are 3 vendors I want to talk to about this possibility, wouldn't it be fun to build?

Gotta go for a few days, going to the Runoffs in 5 minutes.

[john.p.clegg]

Do superchargers have lag?

John

[elansprint71]

Do superchargers have lag?

John

A lot of old lags have had superchargers.

[rgh0]

The biggest challenge will be the flexibility of the head and maintaining the head gasket seal with the higher combustion pressures of a turbo engine. It is hard enough to keep a good head gasket seal on a competition normally aspirated engine with substantially lower pressures than an turbo unit.

You would want to start with one of the newly cast heads I would think

cheers
Rohan

[gus]

I would think a supercharger would be a good fit for a twink, with so many small ones about now, you wuold probably find one that just needs an adapter to the head.

[Tahoe]

I would not go own the road of a supercharger. The belt tension would be a big issue with the Twinks water pump (unless you run 2 belts), plus turbo technology has advance so much in the last few years that lag is just about non existent. So if lag isn't an issue, and cooling and charge cooling isn't an issue, then we're looking only at a head gasket problem. No matter how you look at it, everything involved in making it work properly becomes very expensive. If boost is limited to 6-7 psi I do believe it can be done without any problems, but is it worth it? Probably not, but it would be fun. Before even thinking about forced induction I would go down the road of fuel injection and then start thinking about a turbo. I'm still going to look into it, and maybe with a little help from a few suppliers can make the cost bearable, but I won't hold my breath.

[gus]

A blower the size of the Moss MGB kit would most likely fit in an Elan

Plumbing a turbo in an Elan without cutting glass seems unlikely

Two belts seems like an easy engineering solution, or a bearing support or....

Modern lag free turbos are computer controlled and fuel injected. Not what one would call a simple retrofit

[Chancer]

A couple of points regarding increased combustion pressure and bearing loads.

If I have got this wrong its because of a failing memory, what I recall is from lots of reading and research 20+ years ago and I dont have the time to re-read the books even if I could remember where they are

Anyway I am sure that I can recall of reading about common forced induction myths including perhaps the two above.

I am pretty sure that for the same RPM the bearing loading was actually less on a forced induction car as the pressure on the piston (I have forgotten the term, something like BMEP) was more constant, or perhaaps that should read less pressure reversals, it was all to do with the induction stroke that would normally have a negative pressure and with forced induction positive.

Regarding the combustion pressure and head gasket loading, well the compression ration is correspondingly reduced to end up with IIRC a similar combustion pressure or detonation would destroy the engine unless special fuels were used.

Forced induction is all about increased volumetric efficiency (breathing) higher torque at any given speed without the need to rev the engine higher which is what usually causes tuned engines to let go, On the other hand higher voluletric efficiency means more fuel air mixture and greater power so I can see that logically there must be more combustion pressure being resisted by the head gasket.

I would love to hear your comments which may help blow away the cobwebs clouding my brain, I think the what I read and think that I recall may have been written by David Vizard.

[rgh0]

Yes bearing loads are mainly due to inertia loads from the weight of pistons and rods as they change direction at the end of the stroke top and bottom, the bearing loads due to combustion pressures are substantially smaller. A high rpm racing engine suffers much higher bearing load increases due to higher inertia forces than a similar hp turbo or super charged engine achieving the same power but at lower engine speed. The pressure on the piston at the top of the induction stroke in a pressure charged engine also reduces the inertia load at this point but it does not really make much difference at the other 3 top and bottom points in the 4 stroke cycle.

Combustion pressures however increase much more in a turbo or supercharged engine in order to achieve that higher power and much greater torque at lower revs than you do in a race engine. A 180 hp turbo charge twin cam achieving that power at 6000 rpm and maximum torque at say 4000 rpm will have close to 100% increased combustion pressure compared to a standard twin cam and maybe 70% increase over a competition twin cam which only develops about a 20 to 30 % increase in combustion pressures. This is why turbo charging or super charging has never really worked on a twink as far as I can tell.

The head just manages to seal in normal use. It caused Lotus a lot of work in its development to get it to stop blowing head gaskets. Competition engines with maybe a 20 or 30% increase in combustion pressures struggle without ARP bolts and studs, extra torque on the head bolts and good quality modern composite gaskets to reliably seal.

cheers
Rohan

[Chancer]

I remember competing against another Westfield 7 back in the late 80's that had a turbocharged Lotus twin cam engine, it was seriously quick, dont know about the reliability but it didnt blow that day!

The exhaust, intercooler and intake plumbing was superb, if it can be done in that tiny space then it must be possible Under the bonnet of an Elan.

[john.p.clegg]

I think it was 2006 when I fitted a "blower" driven off the crankshaft...went like stink but the drive was problematic...

John