Speed Six Rebuild: Power 4.3 or 4.5?
Discussion
jcpgasoline said:
Well, I'm convinced. 4.5 it is. Any idea how much torque & how many ponies I should expect from a de-catted 4.5 with ACT Airbox (incl trumpets)?
I would be very suprised if you didn't get 400 HP at the rear wheels from a Tuscan S. I have the airbox but no idea what difference it will make.
Hi there,
I suppose you won't be disappointed when going for the 4.5... When at the continental meeting got a chance to drive Dom's demonstrator. Felt so much more composed and tight compared to my 4.0 sag.
Also very driveable and still nice linear power delivery through the rev range.
When a rebuilt is due I won't have to think about what route to go for! (although 5.0Lturbo charged would be nice for the willie waving concerts in the pub)
Drive the demonstrator and treat yourself well!
I suppose you won't be disappointed when going for the 4.5... When at the continental meeting got a chance to drive Dom's demonstrator. Felt so much more composed and tight compared to my 4.0 sag.
Also very driveable and still nice linear power delivery through the rev range.
When a rebuilt is due I won't have to think about what route to go for! (although 5.0Lturbo charged would be nice for the willie waving concerts in the pub)
Drive the demonstrator and treat yourself well!
jcpgasoline said:
Well, I'm convinced. 4.5 it is. Any idea how much torque & how many ponies I should expect from a de-catted 4.5 with ACT Airbox (incl trumpets)?
Power Graph from TVR Power's website for the 4.3 upgrade here...
http://tinyurl.com/5ts9f74
offers a 5-year 100k-mileage warranty too - you can't argue with that.
Graph shows peak power at about 6250rpm
http://tinyurl.com/5ts9f74
offers a 5-year 100k-mileage warranty too - you can't argue with that.
Graph shows peak power at about 6250rpm
OK....... thank you for that information.
But here is the thing.
Now I believe that what Dom has done is fantastic, I really do.
But as an example.
I was with John Sleath Race Engines on Wednesday and he and I where finalising the 1000Rpm to 2300Rpm extreme "light-throttle" mapping on my Tuscan.
I then got a bit excited and before I new it my rev limiter had kicked in at 7250Rpm............ OK so the motor is built to go there all day. But it is not making any more power up there, that all finished at 6200Rpm.
Now the figures for the Speed Six engine seem to change every time I read a thread about them.
I think that it needs to be put into perspective. As I say it is a mighty fine engine now.
But to quote 7750Rpm as though that has some gravitas is bonkers.
Praise the engine by all means, but keep it grounded in reality.
It is important for people coming to this thread to understand the fine engineering now attributed to this engine. There is no need to over egg the situation. From the graph above the max power is at 6250rpm............ why would one continue to rev the nuts out of the bottom end beyond that? Would not a gear change be a better option? You want to be coming back into the next gear at maximum torque.
Has anyone yet plotted the inter-gear ratios for this set up?
I do not know if the 4.5 graph is markedly different. I would think not though.
Regards.
Speed eight.
But here is the thing.
Now I believe that what Dom has done is fantastic, I really do.
But as an example.
I was with John Sleath Race Engines on Wednesday and he and I where finalising the 1000Rpm to 2300Rpm extreme "light-throttle" mapping on my Tuscan.
I then got a bit excited and before I new it my rev limiter had kicked in at 7250Rpm............ OK so the motor is built to go there all day. But it is not making any more power up there, that all finished at 6200Rpm.
Now the figures for the Speed Six engine seem to change every time I read a thread about them.
I think that it needs to be put into perspective. As I say it is a mighty fine engine now.
But to quote 7750Rpm as though that has some gravitas is bonkers.
Praise the engine by all means, but keep it grounded in reality.
It is important for people coming to this thread to understand the fine engineering now attributed to this engine. There is no need to over egg the situation. From the graph above the max power is at 6250rpm............ why would one continue to rev the nuts out of the bottom end beyond that? Would not a gear change be a better option? You want to be coming back into the next gear at maximum torque.
Has anyone yet plotted the inter-gear ratios for this set up?
I do not know if the 4.5 graph is markedly different. I would think not though.
Regards.
Speed eight.
jcpgasoline said:
Well, I'm convinced. 4.5 it is. Any idea how much torque & how many ponies I should expect from a de-catted 4.5 with ACT Airbox (incl trumpets)?
Not enough as you want. (Willy waving contest kick in the ba.. for a certain Mr. Dom Trickett, for saying that me not making it to Zolder, due to work commitments, was an excuse) 
wouldn't know at what revs my standard 4.0S makes its max power but I do notice that going from 6000 to 7000 revs there is an extra surge, it's like a small turbo is kicking in, fantastic. And it won't stop revving, you have to be careful and quickly change gear at 7000-ish.
so what is the max power a 4.5 makes these days? there is a 4.3 (by Str8six) that makes about 480 bhp at the fly so the 4.5 should brake 500 bhp by now?
so what is the max power a 4.5 makes these days? there is a 4.3 (by Str8six) that makes about 480 bhp at the fly so the 4.5 should brake 500 bhp by now?
Edited by GT TVR on Friday 24th June 16:14
Just a moment......stop the bus!
Below is a typical 4.0Lt standard Six motor................
This gives a BMEP as follows.
HP x Constant (13000) / Litres x Rpm. =
345 x 13000 / 4 x 6250 =
4485000 / 25000 = BMEP of 179........ this is equivalent to the very best production engines
So you can see already how good 179 is.
Now if you are going to take a 4.5 to the 500Hp mark let us look at that equation.
500 x 13000 / 4.5 x 6250 =
6500000 / 28125 = BMEP of 231............ That is formula balls out racing specs !
A) Is this really possible for the Speed Six engine.
B) Would this produce a usable engine for the street?
Regards.
Speed eight.
Below is a typical 4.0Lt standard Six motor................
This gives a BMEP as follows.
HP x Constant (13000) / Litres x Rpm. =
345 x 13000 / 4 x 6250 =
4485000 / 25000 = BMEP of 179........ this is equivalent to the very best production engines
So you can see already how good 179 is.
Now if you are going to take a 4.5 to the 500Hp mark let us look at that equation.
500 x 13000 / 4.5 x 6250 =
6500000 / 28125 = BMEP of 231............ That is formula balls out racing specs !
A) Is this really possible for the Speed Six engine.
B) Would this produce a usable engine for the street?
Regards.
Speed eight.
Speed eight said:
Just a moment......stop the bus!
Below is a typical 4.0Lt standard Six motor................
This gives a BMEP as follows.
HP x Constant (13000) / Litres x Rpm. =
345 x 13000 / 4 x 6250 =
4485000 / 25000 = BMEP of 179........ this is equivalent to the very best production engines
So you can see already how good 179 is.
Now if you are going to take a 4.5 to the 500Hp mark let us look at that equation.
500 x 13000 / 4.5 x 6250 =
6500000 / 28125 = BMEP of 231............ That is formula balls out racing specs !
A) Is this really possible for the Speed Six engine.
B) Would this produce a usable engine for the street?
Regards.
Speed eight.
Speed Eight, I'm checking that I understand your calculations... Your results are in lbf/in2?Below is a typical 4.0Lt standard Six motor................
This gives a BMEP as follows.
HP x Constant (13000) / Litres x Rpm. =
345 x 13000 / 4 x 6250 =
4485000 / 25000 = BMEP of 179........ this is equivalent to the very best production engines
So you can see already how good 179 is.
Now if you are going to take a 4.5 to the 500Hp mark let us look at that equation.
500 x 13000 / 4.5 x 6250 =
6500000 / 28125 = BMEP of 231............ That is formula balls out racing specs !
A) Is this really possible for the Speed Six engine.
B) Would this produce a usable engine for the street?
Regards.
Speed eight.
What utter rubbish knock a 100 bhp off of those numbers and you`ll be about right, S makes max power @6800 rpm.
GT TVR said:
wouldn't know at what revs my standard 4.0S makes its max power but I do notice that going from 6000 to 7000 revs there is an extra surge, it's like a small turbo is kicking in, fantastic. And it won't stop revving, you have to be careful and quickly change gear at 7000-ish.
so what is the max power a 4.5 makes these days? there is a 4.3 (by Str8six) that makes about 480 bhp at the fly so the 4.5 should brake 500 bhp by now?
so what is the max power a 4.5 makes these days? there is a 4.3 (by Str8six) that makes about 480 bhp at the fly so the 4.5 should brake 500 bhp by now?
Edited by GT TVR on Friday 24th June 16:14
Sagaris used to rev to 7500. Harder to tell with the tuscan, I assume the same, but there definitely is power above 7000 where peak power is.
Some engines drop off a cliff after peak power, not the 4.0S.
Just because it's past it's peak doesn't mean it's not making good power. A degree of 'over-rev' is useful in the lower gears to avoid hitting the limiter and on the track too as it can mean hanging on to a gear down a short straight rather than going for 2 extra gearchanges.
Mine produced 326bhp at the wheels at peak but still over 300 past 7000.
Some engines drop off a cliff after peak power, not the 4.0S.
Just because it's past it's peak doesn't mean it's not making good power. A degree of 'over-rev' is useful in the lower gears to avoid hitting the limiter and on the track too as it can mean hanging on to a gear down a short straight rather than going for 2 extra gearchanges.
Mine produced 326bhp at the wheels at peak but still over 300 past 7000.
Maybe Bernie could just use these engines in the Formula 1 season next year ;-)
I am sure the 4.3 and 4.5 S6's are more powerful than a decent build 4ltr but the differences just seem much too big to reconcile - so I wonder if the high RR readings are down to a combo of dyno type (a generous one?), diff (could the different diffs 'help'), tyre slip (TVRs have relatively narrow rear tyres) and the losses calc applied?
I am sure the 4.3 and 4.5 S6's are more powerful than a decent build 4ltr but the differences just seem much too big to reconcile - so I wonder if the high RR readings are down to a combo of dyno type (a generous one?), diff (could the different diffs 'help'), tyre slip (TVRs have relatively narrow rear tyres) and the losses calc applied?
With all these engines being taken out for a full rebuild 4.3, 4.5, FFF why has no-one bothered to put one on a proper engine dyno to get the real figures once and for all and stop all this willy waving ???
Every time a graph gets posted it's the same old same old arguments (of which I for one am really bored now)
There must be at least one engine dyno in the country accessible to the 'public' ?
If I ever get (or need) my engine re-built, I vow to put it on an engine dyno (if accessible and I can afford it !)
Every time a graph gets posted it's the same old same old arguments (of which I for one am really bored now)
There must be at least one engine dyno in the country accessible to the 'public' ?
If I ever get (or need) my engine re-built, I vow to put it on an engine dyno (if accessible and I can afford it !)
RedSpike66 said:
With all these engines being taken out for a full rebuild 4.3, 4.5, FFF why has no-one bothered to put one on a proper engine dyno to get the real figures once and for all and stop all this willy waving ???
Every time a graph gets posted it's the same old same old arguments (of which I for one am really bored now)
There must be at least one engine dyno in the country accessible to the 'public' ?
If I ever get (or need) my engine re-built, I vow to put it on an engine dyno (if accessible and I can afford it !)
I intend to do exactly this when I get my car back and it has been run-in and mapped...Every time a graph gets posted it's the same old same old arguments (of which I for one am really bored now)
There must be at least one engine dyno in the country accessible to the 'public' ?
If I ever get (or need) my engine re-built, I vow to put it on an engine dyno (if accessible and I can afford it !)
jcpgasoline said:
RedSpike66 said:
With all these engines being taken out for a full rebuild 4.3, 4.5, FFF why has no-one bothered to put one on a proper engine dyno to get the real figures once and for all and stop all this willy waving ???
Every time a graph gets posted it's the same old same old arguments (of which I for one am really bored now)
There must be at least one engine dyno in the country accessible to the 'public' ?
If I ever get (or need) my engine re-built, I vow to put it on an engine dyno (if accessible and I can afford it !)
I intend to do exactly this when I get my car back and it has been run-in and mapped...Every time a graph gets posted it's the same old same old arguments (of which I for one am really bored now)
There must be at least one engine dyno in the country accessible to the 'public' ?
If I ever get (or need) my engine re-built, I vow to put it on an engine dyno (if accessible and I can afford it !)
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