Discussion
The speed 6 - it seems to be in all new TVR's, and clearly isnt and doesnt sound like a V8.
Im not very knowlegable re: engine related matters, but did someone once say the reason was because emission regulations were more easily met with a V6 than a V8?? Is that why none of the new TVR's have a V8?
Im not very knowlegable re: engine related matters, but did someone once say the reason was because emission regulations were more easily met with a V6 than a V8?? Is that why none of the new TVR's have a V8?
IRC it was mainly because the RV8 and AJP V8 were both two valve per cylinder units, this (for technical reasons...) means higher emissions, although if I recall either the Ford or Corvette V8 block is also - but does pass worldwide emissions tests 
The RV8 was designed before emissions even existed and the AJP was designed as a race engine, so the emissions weren't so much of a problem.
The S6 has four valves per cylinder, and I beleive its emission levels are low enough for worldwide domination!
The RV8 was designed before emissions even existed and the AJP was designed as a race engine, so the emissions weren't so much of a problem.
The S6 has four valves per cylinder, and I beleive its emission levels are low enough for worldwide domination!
ukbob said:
The speed 6 - it seems to be in all new TVR's, and clearly isnt and doesnt sound like a V8.
Im not very knowlegable re: engine related matters, but did someone once say the reason was because emission regulations were more easily met with a V6 than a V8?? Is that why none of the new TVR's have a V8?
S6 is much cheaper to make than the AJP by all accounts I've heard. And the AJP is lousy on emissions. In comparison, my S6 is de-catted and should, I'm told by TVR, still get through the emissions test with its new ECU in
Straight 6 vs. V8 shouldn't really have a major difference in emissions, all other things (i.e. petrol consumption, etc.) being equal. Power delivery and character is different, though. Most V8s need balancing, meaning worse throttle response, whereas a straight 6 is naturally balanced. The AJP is a bit different cos of its design (75 degree and crank), mind...
And if you don't think an S6 sounds like a V8, you should hear my Tusc; even at idle it's got a lovely bu-bu-bu-bu-bu-bu-bu noise now (took a bit of time and money to get it that way, nind). Not as nice a Griff yet, but as nice as a Cerb in my opinion.
J_S_G said:
[quote=ukbob]
whereas a straight 6 is naturally balanced. The AJP is a bit different cos of its design (75 degree and crank), mind...
Are you kidding?? The Speed Six balanced? Its shakier than a rampant rabbit.
See that big black round thing on the front of the crank, thats a viscous damper, that is.
This is needed cos otherwise the engine would shake the car to pieces at idle.
Andy
andytk said:
Are you kidding?? The Speed Six balanced? Its shakier than a rampant rabbit.
See that big black round thing on the front of the crank, thats a viscous damper, that is.
This is needed cos otherwise the engine would shake the car to pieces at idle.
"a straight 6" is naturally balanced. Now, "TVR's straight six" might not be. That's something entirely different.
the dodger said:
Hmmm. Maybe they got the firing order wrong because a straight six should be naturally balanced.
Wonder why it's so bad? -
I THINK it's something to do with it having a flat plane crank. The firing order is different which means they can get more power out of it.... but I'm probably wrong.... I just remember somebody saying something about it.
A flat plane crank in s straight 6! [is there a smiley for slapping forehead with palm of hand in despair]
The AJP V8 has a flat plane crank. This means when you lay it on a bench it's flat - i.e.none of the big ends are other than 180 degees from one another, so 4 are 'up' and 4 are 'down'.
Split between the 2 banks of a V8 this means 2 pistons are up and 2 are down in each bank - so each bank works like a regular in-line 4. OK so far? However, with a flat plane crank and the V at 75 degrees, the 'up' and 'down' of each piston 'pair' in each bank is 75 degees out relatively. So imagine 2 conventional 4 cylinder lumps running together, but with top dead centre being 75 degrees out of phase on each bank.
Most V8s (Rover, Chevy, Ford) aren't like this, and the pistons (and firing) is equal over all banks i.e. 8 pretty even 'bangs' for every 2 revolutions. In order to achive this, the big ends aren't all just 180 degrees out, but are 90 degrees out (or offset depending on the V), so the crank isn't 'flat' - i.e. if you lie it on a bench some of the big end bearings will stick up.
The advantage of the flat plane is that each bank of 4 runs like a separate 4 cylinder engine to take advantage of exhaust tuning for scavenge...equal shockwaves for each 'bank', with each bank running its own 4-2-1 exhaust.
A flat plane crank in a straight 6? Let me see now. That would mean 3 pistons up and 3 pistons down hmm? Interesting concept. Each 180 degrees we get alternately 2 and 1 piston firing. Or maybe we run 2 pistons up and 4 down...hell if folks don't think the S6 is smooth maybe it's really running all 6 pistons up and down together. A flat plane crank could certainly handle that!
OK, the Laverda Jota 3 cylinder engine ran 2-up and 1-down which gave it a funky beat!
Unless I am mistaken, I think you will find a flat plane crank only makes sense on V8s...or inline 4 cylinder engine (which naturally have flat plane cranks).
WB
The AJP V8 has a flat plane crank. This means when you lay it on a bench it's flat - i.e.none of the big ends are other than 180 degees from one another, so 4 are 'up' and 4 are 'down'.
Split between the 2 banks of a V8 this means 2 pistons are up and 2 are down in each bank - so each bank works like a regular in-line 4. OK so far? However, with a flat plane crank and the V at 75 degrees, the 'up' and 'down' of each piston 'pair' in each bank is 75 degees out relatively. So imagine 2 conventional 4 cylinder lumps running together, but with top dead centre being 75 degrees out of phase on each bank.
Most V8s (Rover, Chevy, Ford) aren't like this, and the pistons (and firing) is equal over all banks i.e. 8 pretty even 'bangs' for every 2 revolutions. In order to achive this, the big ends aren't all just 180 degrees out, but are 90 degrees out (or offset depending on the V), so the crank isn't 'flat' - i.e. if you lie it on a bench some of the big end bearings will stick up.
The advantage of the flat plane is that each bank of 4 runs like a separate 4 cylinder engine to take advantage of exhaust tuning for scavenge...equal shockwaves for each 'bank', with each bank running its own 4-2-1 exhaust.
A flat plane crank in a straight 6? Let me see now. That would mean 3 pistons up and 3 pistons down hmm? Interesting concept. Each 180 degrees we get alternately 2 and 1 piston firing. Or maybe we run 2 pistons up and 4 down...hell if folks don't think the S6 is smooth maybe it's really running all 6 pistons up and down together. A flat plane crank could certainly handle that!
OK, the Laverda Jota 3 cylinder engine ran 2-up and 1-down which gave it a funky beat!
Unless I am mistaken, I think you will find a flat plane crank only makes sense on V8s...or inline 4 cylinder engine (which naturally have flat plane cranks).
WB
Tripps said:according to a newly aquainted factory trained independant source of mine,this engine probably,more than likely,wont be able to satisfy the emmisions regs much longer either.so what next?
The S6 has four valves per cylinder, and I beleive its emission levels are low enough for worldwide domination!
) that the 2006 emissions regulations will require some strangling of the S6.Gassing Station | General TVR Stuff & Gossip | Top of Page | What's New | My Stuff