Sorry Lee, I would not be optimistic of your achieving a 95Db track day noise limit with a 396 engine slightly modded as you say yoiu have, AND that will rev normally in actual driving use. Especially if you are only at 108Db at 3500 at present. I doubt anyone could succeed with that target. There are plenty of track days with 105 Db static test limits and that should be acheiveable but remember the static tests are at 3/4 of max rpm so unless you car redlines at only 4666 rpm (I doubt that!) you need to test at a higher rpm level. I do know of a silencer system that was used on an engine with similar capacity to yours but heavily modified that was used to pass SVA so if you wish I will let you know who has it. I don't know if limits have changed since SVA became IVA though.
Frank Catt Exhaust now fitted.
- Thread starter Lee
- Start date
Glenn M
Supporter
Tell me about it Malcolm, I was driving the car, (not mine), and it did cause a pucker moment to look back and see flames I can tell you! My passenger still has the outright record for a dismount from a 40! The owner not best pleased with that exhaust system as it wasn't cheap and it was also supposed to pass the noise test at Goodwood - which it did not. 118db as I recall ? Engineering definitely not well done!
Frank 900-1000 deg C in the collectors sounds to high.
You would expect max 800c ish at the port, 900 that far down the pipe is hot.
Jim
You would expect max 800c ish at the port, 900 that far down the pipe is hot.
Jim
Jim, this was measured on P1018 , one of the fastest original GT40 race cars in the UK, while testing at Goodwood for the Revival, Frank
Gee your fast with reply Frank.
Regardless there will be a reason.
Those temps something seems a little out of place.
I am surprised the head of the exhaust valve doesn't fall off.
Anyway not our problem
Jim
Malcolm
Not enough ignition timing will drop comustion chamber temp but raise exhaust temp dramaticly.
Back pressure maybe but not likely.
Jim
Not enough ignition timing will drop comustion chamber temp but raise exhaust temp dramaticly.
Back pressure maybe but not likely.
Jim
What criteria are they using to measure these noise levels @ your UK track days, here in NZ they appear to be about 40/60 feet away from trackside @ same height. On JO's TVR we were pinged @ 97db ( Limit 95db ). At this point of track car was @ full throttle @ approx 6500/7000 in third gear just before shift into top IIRC, a slight change in tailpipe direction eliminated that issue ( created another small problem though ) 
Ron Earp
Admin
900C is 1662F. I'd be worried if I saw 1662F on my EGTs where are located a couple of inches out from my exhaust ports. I'd definitely be concerned if I saw 1662F at my muffler.
Is there a possible temperature unit mix up at play here?
Terry Oxandale
Skinny Man
What has the experience been, and is the recomendation for spacing, air flow, and insulating shields or materials for close proximity body panels?
Many moons ago, Robin Batt and I shared a track day at Brands on the GP circuit in my car, but his track day, as his car wasn't ready. We did over 50 hot laps and had a great day. Back then my car was pretty standard GTD spec and ran the louvred grill vents on top of the rear clip and at the back each side of the exhaust opening. This reduced airflow from the engine bay and the inner panelling got too hot. One of the fixings for the body stays pulled through even though it had spreader washers on. The big flat panels warped too but went straight again once they cooled down. I removed the louvre panels on the rear of the car and that allows lots of air flow and solved my problems. But when we have had mental hot days at the track, I now remove the louvre panel on top of the rear clip just to let more heat out. So conclusion is that the 9 hole Le Mans vent on top is a good idea and to run no panels or wire mesh panels only on the rear of the car is my preferred choice now. If you don't track your car you should be able to get away with the louvred panels I would expect.
Another issue that promixity can cause is if you run your throttle cable to the rear of the engine and then up to your carbs. If it gets too hot it will seize up and become rather heavy to use. Or it could stick wide open. Happened to me once when leaving Silverstone in a traffic jam. Multiple lanes of traffic and I am in the thick of it struggling to keep rpm down as the throttle is sticking. Looking a bit of a prat really. Look over to my passenger to chat and guess who I see looking in at us? Only bloody Derek Bell leaving the circuit in his Audi! Aaaagh! FAIL!
Again if you have a cable gear shift system as on a GTD you really need to insulate it thoroughly with heat sheild panels and sleeving. That will keep it running smoothly but you do need to pay attention to it.
If you do not repack your silencers regularly, then the empty silencer can resonate. On GTD exhaust systems, particularly the non cross over system, the silencer can fatigue and split open underneath. Then really hot gases come out. This is what happened to one of the cars I mentioned above. The hot gases set fire to the number plate. If your car is rasping, I would suggest you check for a split. On a GTD it is an easy fix to weld the split up or plate it as the silencer box is quite thick guage metal. But repack it too!
I would recommend a reflective heat lining material is glued to the underside of any rear clip to keep heat transfer to the paint down to a minimum. This will occaisionally need re gluing as I have yet to find a perfect glue that can cope with the temps I get under my rear clip. GTD actually used to put a heat resisiting layer of something into the bodywork in manufacture as an option. I choose this and prior to paint you could see a 1/8 inch thickness of white in the fibre glass build up. If the width of the plenum area and then back to the duck tail spoiler seems a bit thick on your GTD, it could easily be because of this heat resisiting panel insert.
For exhaust issues I think that is most things that would concern me and my experiences in dealing with them. Of course you then get engine heat issues for fuel, heat soak into the carbs, hot air supply, rear window (if plastic) deforming, oil coolers, etc etc.
You need to talk to some TVR dealers or independent garages. All TVRs use a heat shield matting that is glued to the engine bay side walls. I have had my TVR for about 7 years and the car is about 12 years old and that matting is still well and truly stuck in place.
Malcolm
On my old GTD I had issues with the throttle cable and it took ages to sort it out. I kept the routing round the back of the engine but used eventually a Venhill kit car cable with a teflon linner. That was covered in a reflective fabric tube and then a length of cool tube. This worked a treat and has done for three years now. I have done exactly the same on my new car so fingers crossed it will be fine.
The rear clip on my old car had a reflective foil glued in place and never moved despite being seriously hot on occasion. It was on the car when I purchased it so have no idea what it was or what glue was used. One thing that does help is cermachroming the exhaust. This keeps the heat in the pipe and gasses so will reduce heat build up in the rear clip, as long as the silencers don't strangle the engine and cause heat to build up.
Martin
On my old GTD I had issues with the throttle cable and it took ages to sort it out. I kept the routing round the back of the engine but used eventually a Venhill kit car cable with a teflon linner. That was covered in a reflective fabric tube and then a length of cool tube. This worked a treat and has done for three years now. I have done exactly the same on my new car so fingers crossed it will be fine.
The rear clip on my old car had a reflective foil glued in place and never moved despite being seriously hot on occasion. It was on the car when I purchased it so have no idea what it was or what glue was used. One thing that does help is cermachroming the exhaust. This keeps the heat in the pipe and gasses so will reduce heat build up in the rear clip, as long as the silencers don't strangle the engine and cause heat to build up.
Martin
Thanks for those tips guys. My current throttle cable is an Historic F1 cable (allegedly!) that runs up the front of the engine now so 2 ft from the exhaust. Worked fine for 10 years. Also allegedly it is good for up to 1000c. Hey maybe I should sell one to Frank to put on the 40 his exhaust was hot on! I hear lorry throttle cables are quite good for being tough and of good quality if you can get the length and fittings right.
Keep meaning to do something with the heat material glue, but just never get round to it. Clealry Martin you still weren't going quick enough to build up enough heat to peel the foil off your GTD.......
I hear lorry throttle cables are quite good for being tough and of good quality if you can get the length and fittings right.Keep meaning to do something with the heat material glue, but just never get round to it. Clealry Martin you still weren't going quick enough to build up enough heat to peel the foil off your GTD.......
Now Now Malcolm!!!
Not fast enough hey?
Are you going to enter for the Isle of Man Classic in April?
We will see who is fast then if you can make it.
Us Northern boys will show you southern jessies a thing or two.
Kindest Regards Martin.
Not fast enough hey?
Are you going to enter for the Isle of Man Classic in April?
We will see who is fast then if you can make it.
Us Northern boys will show you southern jessies a thing or two.
Kindest Regards Martin.
What criteria are they using to measure these noise levels @ your UK track days, here in NZ they appear to be about 40/60 feet away from trackside @ same height. On JO's TVR we were pinged @ 97db ( Limit 95db ). At this point of track car was @ full throttle @ approx 6500/7000 in third gear just before shift into top IIRC, a slight change in tailpipe direction eliminated that issue ( created another small problem though )
Most track days in the UK have either a 98db or 105db limit measured static at 3/4 of max rpm at 45 degrees 1/2 metre from the tail pipe. This is usually a compulsory test before going out onto the track. There can also be track side noise meters with a limit that is less than the static test one. The max rpm stated to the noise tester can be subject to some interpretation, eg GT40s usually seem to have a max of 5,000 rpm. Also noise testers often don't understand the rpm reading indicated by coloured lights on the steering wheel. However, the track side meters will always get you if you are too noisy.
I would have thought it was almost impossible to get a GT40 with tuned engine down to 98db without an exhaust that was very restrictive on gas flow. This in turn might lead to the heat build-up problems mentioned elsewhere in this thread.
Chris
Unlikely to go to IoM, anyway think I won all rounds there already over the years bar the big one, Llergy Frissel but that is just a power run really, no real skill involved!!!!! Sloc and Creg Ny Ba were my speciality. Mind you if I finish my MX5 project in time it would do well there, but then I suppose it would be bad form to beat you northerners in your real Man's car whilst I am in a hairdressers car.
The first year we went to IoM, we were on the ferry and the place was covered in snow! Walking Llerghy Frissel we built snow men at each turn in point as markers but the buggers had melted by the time the event started. I remember being on the start line at The Sloc watching the snow starting to come down, when a marshal came over and asked me to turn on my headlights so the finish line marshals could see me coming. Not only was it snowing but the clouds had come down below the finish line altitude! And I was on slicks.....
However I may be tempted at some time to get my car back in the GTD series to see how well Mick's Southern GT chassis work has improved the car. Only way to tell is by competition with timed runs where I have competed before. We shall see.
On the track noise testing thing, Chris, I thought the distance was 1 metre not 0.5 metres, but I could be wrong on that as haven't been static tested for a while now. Mick has made me a super set of megaphones which clearly won't pass any noise test on the planet, but I am keen to try them at least once somewhere (where accepted) 'cos they sound flipping fantatsic! I wonder what level they would test at? It would fun to measure them one day.
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