Under bonnet heat - S2

[Maulden7]

In extremes of ambient temperature & heavy slow moving / static traffic, my S2 can suffer from high engine temperatures after 45 minutes or so i.e. the guage goes off the scale & into the oil pressure section! The temperature holds fine for 20 minutes or so, the electric fan cuts in at 80degF (& blows in the right direction!!) but if no exterior air flows through the rad with the car on the move the temperature then continues to climb.

If I don't stop & open the bonnet the engine will stop running due to fuel vaporisation, but 20 minutes with the bonnet up, the temperature drops quickly, everything is fine, & off you go. On the move the temperature remains at 70/80degF even under the hardest driving conditions & hot weather.

I have a full width ally rad / swirl pot arrangement (from TT) & there is no coolant loss whatsoever after this extreme temperature situation happens. The cooling system itself is in good condition, but this has only started since I fitted a big bore extractor manifold & exhaust system (also from TT) The engine is built to deliver around 150bhp, & I have no doubt that under bonnet temperatures are higher now than they were before I fitted this efficient manifold / system (for obvious reasons - the first time out some of the plastic pipes in the vicinity of the manifold melted & I have subsequently wrapped everything nearby with heat reflecting material for protection)

My conclusion is that the heat generated under the bonnet is unable to escape, & simply builds up, creating a "runaway" situation.

I believe that later cars had "heat escape" vents set into the top of the engine compartment to vent into the wheel arches. Is this correct, & if so could somebody please post some pics of where these are? If these vents are cut into the sides, would it also help to rig up a small 12v extractor fan on one side connected to the main fan?

Thanks for any thoughts.

Dave M.

[Coupe]

Dave
I have the same TTR manifold and exhaust as you (we met at the EALC Elan photo session last year at Rushall) I have not had a problem with excessive heat but my 66 Coupe does have two vents as shown in photo which originally had a fine gauze over both (or maybe Evans waterless coolant is more efficient then water !!!)
Ben

[trw99]

Discussed before and with photos here: lotus-suspension-f42/wheel-arch-holes-for-improved-cooling-t18914.html

Tim

[Maulden7]

Thanks chaps, just what I wanted to see / read.

Now ......... where's the drill & hole cutters?!

Dave M.

[john.p.clegg]

Dave
Before you start hacking at your plastic (there is a damn big hole under the engine),have you stuffed all the gaps around the radiator ? (over the steering rack/between the rad. and bonnet etc )

John

P.S.
Ben,where does that pipe from your stat. housing go?

[cabc26b]

Dave ,

Are your headers coated ? i run a similar set up with out the high ambient - my headers are ceramic ( jet-coat) coated.

George

[Coupe]

P.S.
Ben,where does that pipe from your stat. housing go?[/quote]

John - see photo

Alternator normally has a heat shield but it needs to be re-fitted after a repair.

[Maulden7]

Thanks for the additional responses.

This is not a problem of overheating when on the move, & the rad is a full width ally design (which is of course more efficient than the standard type anyway so even more heat released into the engine bay) No gaps at the sides or the bottom & the top is sealed to the bonnet.

No, the ss manifold is not coated (can you coat ss metal?) & assuming that ss can be coated I agree that this could improve the problem (does this affect the efficiency of the exhaust system?) but the manifold itself was a real bugger to fit with the engine in place (even with one mount unbolted & the other slackened off) so I'm very loathe to take it off again I'm afraid.

Still seems like I need that hole cutter & drill?

[StressCraxx]

Thanks for the additional responses.

No, the ss manifold is not coated (can you coat ss metal?) & assuming that ss can be coated I agree that this could improve the problem (does this affect the efficiency of the exhaust system?) but the manifold itself was a real bugger to fit with the engine in place (even with one mount unbolted & the other slackened off) so I'm very loathe to take it off again I'm afraid.

Still seems like I need that hole cutter & drill?

"No, the ss manifold is not coated (can you coat ss metal?)" - Yes you can. I have a Dave Bean set that I had ceramic coated inside and out. It came out really well. The easiest way to install is to support the engine with a sling on a hoist and remove both mounts. Shove the engine over towards the right side of the chassis and slip them in. Then reinstall the motor mounts on the exhaust side while you have room, the intake side next.

Is your radiator sides, bottom, and top sealed so air will not recirculate back around, or shrouded so it will not recirculate back through?

[Maulden7]

Thanks for the info re coating the ss manifold, learn something new every day.

Re the installation, yes, that's basically what I did, but still some long heavy bars & a lot of "grunting" needed to tilt the engine over! However, despite the tiny clearances once installed, there has never been any contact at all between any part of the exhaust system and anything else.

Is your radiator sides, bottom, and top sealed so air will not recirculate back around, or shrouded so it will not recirculate back through?

The rad & added sealing basically prevents any recirculation, & directs all air flow on the move through the rad (apart from around the cone air filter in the nose & trunking into the standard air box) The nose area is basically sealed off from the engine compartment itself.

Are you suggesting that I should remove some of these "seals"?

Thanks for the interest - Dave M.

[billwill]

Do these holes in the wing let in mud & rain water from the wheel arches?

I can't quite visualise where these holes go, despite the photo.

[Maulden7]

Well, may not please the purists, but the deed is done & it seems to work!





Dave M.

[gusplustwo]

Just as a note, my plus two with a stock motor, small radiator, no water pump fan but a monster Bosch radiator fan will run at idle in any temp [IE95 deg f] until it runs out of gas. for years I have run only a manual switch and occasionally forget to turn it on, resulting in excursions towards the orange zone on the gauge. Turn on the fan and it will pull it down in a few minutes.

My point is, they shouldn't run hot. You create no power, and thus no heat, at idle.

Either your car is retarded at idle, or the new headers are over- extracting at idle and running it lean.

If your car detonates at high end and you are retarding it to compensate, recurve the distributor

[Maulden7]

Thanks for the thoughts.

The engine was set up on a dyno by a very experienced & well known engine builder in the UK, & is built / tuned for sprinting & occasional track work (as is the rest of the car) The car is very fast (well ........ fast enough for me - you can ask others here who have seen it in action) so any alterations need to be thought about very carefully.

Interestingly, before I modified the car to the current spec (so it was then running a standard 105bhp engine rebuilt by myself, stock S2 - large - rad, small bore exhaust with nothing special 4-branch manifold - engine fan - stock ignition) the same thing used to happen.

[gusplustwo]

Race engine tuners rarely pay any attention to idle

Lean at idle

retarded at idle

insufficient fan