Discussion
Why did TVR decide to make the Speed Six engine rather than using the AJP8 in other models? From what little I know, the AJP8 was reliable, characterful and no less powerful than the Speed Six, so what was the problem with it? Was it too big, too expensive, not able to comply with emissions law or something else?
I realise that this is probably a somewhat contentious issue. I'm not trying to start an argument about which is better but I'm genuinely curious about what the company's rationale was.
I realise that this is probably a somewhat contentious issue. I'm not trying to start an argument about which is better but I'm genuinely curious about what the company's rationale was.
IMHO The AJP8 being a very big 2 valve engine with pretty wild cams it was a bit of a future emissions might mare .. so they had to go 4 valve head at some point.. others say that PW wanted that old Aston sound of a straight 6.. maybe they also though it's unit cost might be cheaper too ..
I asked the very same question at the middle wallop talk with Al Melling, his answer was emissions as the large ports of a 2 valve engine have poor gas speed, which reduces in-cylinder motion which reduces combustion efficiency.
Thing is I didn't believe him.
Not that because the above isn't true, but on its own it wasn't reason enough to drop the 8 as with a better ECU and close coupled cats it would have passed emissions easily.
Mainly because theres plenty of 2 valve engines being launched in California, known to have the toughest emissions laws in the world.
So I agree with you, the AJP8 should never have been dropped and could have been offered as an option to the six.
Who knows mabye TVR would still be trading?
Matt
Thing is I didn't believe him.
Not that because the above isn't true, but on its own it wasn't reason enough to drop the 8 as with a better ECU and close coupled cats it would have passed emissions easily.
Mainly because theres plenty of 2 valve engines being launched in California, known to have the toughest emissions laws in the world.
So I agree with you, the AJP8 should never have been dropped and could have been offered as an option to the six.
Who knows mabye TVR would still be trading?
Matt
Well another little gem from middle wallop was that the Rover engine from rover cost TVR about £2800 , whereas the AJP8 including custom bellhousing and clutch cost £3700.
I have to say it sounded like a bargain to me.
apparantly PW wasn't too happy about the extra 900 notes....
What is boils down to is that PW wanted to do a 6 cylinder. And there's not much more rationale behind it.
Matt
I have to say it sounded like a bargain to me.
apparantly PW wasn't too happy about the extra 900 notes....
What is boils down to is that PW wanted to do a 6 cylinder. And there's not much more rationale behind it.
Matt
AJP8, Rough as a badgers arse, what planet are you on? It's far and away the best engine that ever landed in a TVR. Out performs the S6 in every aspect and lasts more than a fortnight too. With it's cats in place and a decent ECU it also meets current regs. Although I do certainly agree that the S6 is cleaner, since it spends most of it's time on the back of a diesel recovery truck.
As for the latest and greatest S6 engines. OK, you can now buy one for £15,000 with a 3 year warranty. Well I'm no rocket scientist but I dont need to be to work out that at £15,000 they have charged you for the next two rebuilds to ensure they can't lose. Now does that inspire confidence?
As for the latest and greatest S6 engines. OK, you can now buy one for £15,000 with a 3 year warranty. Well I'm no rocket scientist but I dont need to be to work out that at £15,000 they have charged you for the next two rebuilds to ensure they can't lose. Now does that inspire confidence?
Sorry alcohol fueled comment 
I know it sounds fantastic and goes like (insert colurful metaphor) and produces an immense amout of power but isn't it by it's nature as a flat plane crank not as smooth as other engines?
That's from my understanding, I'm very happy to be proved wrong if that's the case.
I know it sounds fantastic and goes like (insert colurful metaphor) and produces an immense amout of power but isn't it by it's nature as a flat plane crank not as smooth as other engines?
That's from my understanding, I'm very happy to be proved wrong if that's the case.
SamHH said:
I realise that this is probably a somewhat contentious issue. I'm not trying to start an argument about which is better but I'm genuinely curious about what the company's rationale was.
V8 GRF said:
It's a rough as a badgers arse.
fatjon said:
Out performs the S6 in every aspect and lasts more than a fortnight too. Although I do certainly agree that the S6 is cleaner, since it spends most of it's time on the back of a diesel recovery truck.
And they're of........ The descent into the AJP8/S6 argument again, where the OP even states this is never the intention. I am guessing at some point we are all going to sell our cars and I bet that the brand (and ourselves) suffers from wheeling out the unquantified perceived infallabilities of eachothers cars.
Edited by Moulder on Friday 11th April 13:11
Only baiting the S6 crew, it's a sport you know.
Yes, the AJP is a flat plane crank and they do have slightly more second order vibrations but in a sports car it's really not the highest priority. The crossplane cranks have big power disadvantages in that the balance weights add hugely to the rotating mass and make it very expensive to make them rev high enough for higher outputs (but they sound horny). The firing order also precludes getting good extraction from the exhaust ports. The S6 engine really is quite an acheivement in terms of getting 350BHP out of a 6 pot 4 litre but when you look at the mechanics of it, it really does look like it was designed by a kid with a meccano set. You only have to look at the timing chain arrangement with an engineering eye to see that it's going to break. The valve assembly is the same, you can picture the sideways forces on the valves just by looking at the angle of the followers on the valve/spring assembly. No amount of twiddling with the exact material composition or peeing a bit more oil on it will sort it out. What I do not get is why whoever designed it, be it TVR or Melling, did not run an inverted bucket direct acting cam system, like everyone else does. These engines do not run to extreme RPM or a hugely agressive cam profile so valve motion control is a way off being an issue with them.
Jon
Yes, the AJP is a flat plane crank and they do have slightly more second order vibrations but in a sports car it's really not the highest priority. The crossplane cranks have big power disadvantages in that the balance weights add hugely to the rotating mass and make it very expensive to make them rev high enough for higher outputs (but they sound horny). The firing order also precludes getting good extraction from the exhaust ports. The S6 engine really is quite an acheivement in terms of getting 350BHP out of a 6 pot 4 litre but when you look at the mechanics of it, it really does look like it was designed by a kid with a meccano set. You only have to look at the timing chain arrangement with an engineering eye to see that it's going to break. The valve assembly is the same, you can picture the sideways forces on the valves just by looking at the angle of the followers on the valve/spring assembly. No amount of twiddling with the exact material composition or peeing a bit more oil on it will sort it out. What I do not get is why whoever designed it, be it TVR or Melling, did not run an inverted bucket direct acting cam system, like everyone else does. These engines do not run to extreme RPM or a hugely agressive cam profile so valve motion control is a way off being an issue with them.
Jon
fatjon said:
The valve assembly is the same, you can picture the sideways forces on the valves just by looking at the angle of the followers on the valve/spring assembly. No amount of twiddling with the exact material composition or peeing a bit more oil on it will sort it out. What I do not get is why whoever designed it, be it TVR or Melling, did not run an inverted bucket direct acting cam system, like everyone else does.
Moving the followers off centre was one of the major upsetting things that TVR did in the AJP6 to Speed6 transition according to the MW talk.Such a small change and it was probably responsible for the failure of the company, what with blow ups damaged reputation and warranty claims. Anyway, I agree that we are getting rather off topic here.
To get back on topic, my votes for the engines.
1. AJP for its sheer b
ks, and for TVR proving that the brits can still do world class engines.
2. RV8 in its bigger capacities for fantastic sound and nearly as much power plus bottom end grunt.
3. S6 for punching well above its weight as a six pot 4.0, if only briefly...
4. Ford v6 engines in various guises for costing sweet FA to fix so you dare actually thrash them.
To get back on topic, my votes for the engines.
1. AJP for its sheer b
ks, and for TVR proving that the brits can still do world class engines.2. RV8 in its bigger capacities for fantastic sound and nearly as much power plus bottom end grunt.
3. S6 for punching well above its weight as a six pot 4.0, if only briefly...
4. Ford v6 engines in various guises for costing sweet FA to fix so you dare actually thrash them.
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