Speedsix crank timing
Discussion
Hi Peeps
An exhaust specialist has suggested that I may be able to quieten the noise on my S6 powered kit car by changing the silencers and adding a crossover to connect the two exhausts. The engine is running a stock TVR exhaust manifold, but the rest of the exhaust is non standard. I'm trying to work out if the cross over would add enough value as its proving quite expensive.
My thinking is that if the engine is designed with pots 1,2 & 3 hitting TDC 120 degrees out, and pots 4,5 & 6 hitting TDC at the same time as 1-3 then joining the exhausts will add nothing as the pressure pulses from each side arrive at the same time.
I haven't been able to find a description of the crank timiing on the net. Can anyone help?
TIA
An exhaust specialist has suggested that I may be able to quieten the noise on my S6 powered kit car by changing the silencers and adding a crossover to connect the two exhausts. The engine is running a stock TVR exhaust manifold, but the rest of the exhaust is non standard. I'm trying to work out if the cross over would add enough value as its proving quite expensive.
My thinking is that if the engine is designed with pots 1,2 & 3 hitting TDC 120 degrees out, and pots 4,5 & 6 hitting TDC at the same time as 1-3 then joining the exhausts will add nothing as the pressure pulses from each side arrive at the same time.
I haven't been able to find a description of the crank timiing on the net. Can anyone help?
TIA
Edited by SkyUK on Monday 22 October 13:16
cam timing is for an s spec engine 113 inlet and 107 ex, I think, and standard is something like 107inlet and 106 ex have info at home but this is all from memory.(which is `iffy at best of times).
I am doing the same thing on my sagaris at the moment, and I am going to fit a cross over pipe as an experiment to see if it will quieten down a little without effecting an power outputs, you can get a stainless cross pipe for £30 on fleabay, but you`ll probably have to change your pipe work to suit the distance between pipe centers on the cross pipe, ideally you should try and position it as close to the manifolds as possible, not so easy on a tvr but possibly easier on a kit car if you have the space?
firing order is 135246
I am doing the same thing on my sagaris at the moment, and I am going to fit a cross over pipe as an experiment to see if it will quieten down a little without effecting an power outputs, you can get a stainless cross pipe for £30 on fleabay, but you`ll probably have to change your pipe work to suit the distance between pipe centers on the cross pipe, ideally you should try and position it as close to the manifolds as possible, not so easy on a tvr but possibly easier on a kit car if you have the space?
firing order is 135246
Edited by clive f on Monday 22 October 14:11
clive f said:
cam timing is for an s spec engine 113 inlet and 107 ex, I think, and standard is something like 107inlet and 106 ex have info at home but this is all from memory.(which is `iffy at best of times).
I am doing the same thing on my sagaris at the moment, and I am going to fit a cross over pipe as an experiment to see if it will quieten down a little without effecting an power outputs, you can get a stainless cross pipe for £30 on fleabay, but you`ll probably have to change your pipe work to suit the distance between pipe centers on the cross pipe, ideally you should try and position it as close to the manifolds as possible, not so easy on a tvr but possibly easier on a kit car if you have the space?
firing order is 135246
Thanks, but I'm after crank timing not cam timing so I can visualise the pressure pulses in each pair of pipes and logically establish whether a crossover would make any difference.I am doing the same thing on my sagaris at the moment, and I am going to fit a cross over pipe as an experiment to see if it will quieten down a little without effecting an power outputs, you can get a stainless cross pipe for £30 on fleabay, but you`ll probably have to change your pipe work to suit the distance between pipe centers on the cross pipe, ideally you should try and position it as close to the manifolds as possible, not so easy on a tvr but possibly easier on a kit car if you have the space?
firing order is 135246
Edited by clive f on Monday 22 October 14:11
try this, qouted from RND engineerings website.
"The cylinders are in pairs 120 degrees apart and are firing as 1 & 6, 2 & 5 and then 3 & 4. As each pair reach tdc one cylinder will be exhausting, then once over tdc it will be on induction, whilst the other will still be on compression, followed by its power stroke once over tdc. On one 360 degree rotation of the crank each pair of cylinders will go through the above cycle. "
"The cylinders are in pairs 120 degrees apart and are firing as 1 & 6, 2 & 5 and then 3 & 4. As each pair reach tdc one cylinder will be exhausting, then once over tdc it will be on induction, whilst the other will still be on compression, followed by its power stroke once over tdc. On one 360 degree rotation of the crank each pair of cylinders will go through the above cycle. "
clive f said:
try this, qouted from RND engineerings website.
"The cylinders are in pairs 120 degrees apart and are firing as 1 & 6, 2 & 5 and then 3 & 4. As each pair reach tdc one cylinder will be exhausting, then once over tdc it will be on induction, whilst the other will still be on compression, followed by its power stroke once over tdc. On one 360 degree rotation of the crank each pair of cylinders will go through the above cycle. "
Perfect, thanks Clive. So 1 & 6 rise and fall together but when 1 is on compression 6 is on exhaust, etc. So there would be a balancing effect to be gained from a cross over, although maybe not that much."The cylinders are in pairs 120 degrees apart and are firing as 1 & 6, 2 & 5 and then 3 & 4. As each pair reach tdc one cylinder will be exhausting, then once over tdc it will be on induction, whilst the other will still be on compression, followed by its power stroke once over tdc. On one 360 degree rotation of the crank each pair of cylinders will go through the above cycle. "
Remember it takes two full revolutions (ie 720 deg) for all six exhaust pulses to pass through the exhausts, not one. So that means there is one exhaust pulse every 120 degrees if you combined both manifolds together with an X-pipe with no interference (assuming equal lengths of manifold before the x-pipe of course)
dvs_dave said:
Remember it takes two full revolutions (ie 720 deg) for all six exhaust pulses to pass through the exhausts, not one. So that means there is one exhaust pulse every 120 degrees if you combined both manifolds together with an X-pipe with no interference (assuming equal lengths of manifold before the x-pipe of course)
Thanks Dave, thats what I'd figured. I've read further and understand that the standard S6 headers aren't perfect equal length but they'll be good enough for me. I am getting a cross over put in the exhaust to balance the pulses across both silencers, which should help bring the noise down.Very good thread on the subject started by the chap from syvecs
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Walford said:
spitfire4v8 said:
What difference does the injector batch firing make? similarly what cylinders are wasted spark. The only thing that matters is the sequence the exhaust valves open.
Wasted spark is the ignition timmingthis normally runs in time with valve open and closing
Again the ONLY thing that affects the order of the exhaust pulses is the order of the exhaust valves opening.
m4tti said:
Very good thread on the subject started by the chap from syvecs
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
The guy from syvecs actually got the coil info wrong until it was pointed out to him though if you read it. Good threads though all the same on all the syvecs stuff and RG stuff going around at the time. http://www.pistonheads.com/gassing/topic.asp?h=0&a...
spitfire4v8 said:
The guy from syvecs actually got the coil info wrong until it was pointed out to him though if you read it. Good threads though all the same on all the syvecs stuff and RG stuff going around at the time.
Yeah i noticed that.. he was corrected swiftly. Perhaps getting confused by the number of throttle pots or manifolds 
Good thread though minus that little confusion. Dont seem to get many like that now.spitfire4v8 said:
Walford said:
spitfire4v8 said:
What difference does the injector batch firing make? similarly what cylinders are wasted spark. The only thing that matters is the sequence the exhaust valves open.
Wasted spark is the ignition timmingthis normally runs in time with valve open and closing
Again the ONLY thing that affects the order of the exhaust pulses is the order of the exhaust valves opening.
and you would think the valve timming would be the same on all 6 cylinders
so the cylinders that share coils must have valve timming 360' apart
Edited by Walford on Saturday 27th October 17:00
Camshaft Timing Figures. Valve Lift inlet and exhaust .400 thou or 15.75mm .Centreline Angles Standard inlet 107.5 .Inlet Opens 26.5 degrees btdc, closes 61.5 degrees atdc, Standard Exhaust 104.5 opens 58.5 degrees btdc closes 29.5 degrees atdc. R/R S and Sagaris Lift .400 thou or 15.75mm.Inlet CLA 113.5 Inlet opens 20.5 degrees btdc closes 67.5 degrees atdc exhaust CLA 107.5 opens 61.5 degrees btdc closes 26.5 degrees atdc. Duration inlet and exhaust 268 degrees
Gassing Station | Speed Six Engine | Top of Page | What's New | My Stuff