Last edition "4.2" and original 4.5, what's the difference?

[Filos Hippos]

So what is the difference between these two cars or more importantly, engines.

I've been told the latest 4.2's really had the 4.5 bottom end.

Does that mean the difference is in the induction, etc. Or also the heads?

Is there a big difference in power?

[alinton]

And the last 4.5s had the 4.2 inlets, just to confuse things!


So I suspect that the last cars may all have actually been 4.5s, albeit with the 4.2 style inlets.

A,

Edited by alinton on Thursday 9th July 12:54

[plumAJP]

even with the later 4.5 bottom ends, if it has the 4.2 inlets, it will be same bhp as a early 4.2 wouldn't it? 360bhp.

you just have the reliability of a better crank

[alinton]

Well, as long as the capacity was actually 4.5L and not 4.2, of course!

A.

[headcase]

I had a look at 'the last' cerbera when it was at preston, it deffinatly had purple inlet pipes like all of the other 4.5's i have seen.

[Filos Hippos]

are there any advantages in the 4.2 heads compared tot the 4.5's.

Or induction system for that matter?


Or were they just using all the last parts available in the bin...

[Ballsy]

Filos Hippos said:

are there any advantages in the 4.2 heads compared tot the 4.5's.

Or induction system for that matter?


Or were they just using all the last parts available in the bin...

Yup that sounds like TVR lol
There isnt really much difference in power between the models but the 4.5 is easier to tune altho going by what people on here have said TVR seemed to be rather optimistic when it came to original power figures lol.

[SimonKD]

headcase said:

I had a look at 'the last' cerbera when it was at preston, it deffinatly had purple inlet pipes like all of the other 4.5's i have seen.

It does indeed, this picture was taken in Blackpool in July 2006. You can clearly see the purple pipes



Regards
Simon

[fatjon]

Filos Hippos said:

are there any advantages in the 4.2 heads compared tot the 4.5's.

Or induction system for that matter?


Or were they just using all the last parts available in the bin...

No advantage in the heads as they are the same. 4.5 inlet is longer which should make the torque peak lower in the RPM range apart from that there's really not much in it. I think the extra power of the 4.5 is mainly from a bit more CC, 16% more power on paper for 7% more capacity but we all know that the 4.5 rarely makes over 400 without some small mods so assuming 390BHP its 8% more for 7% more capacity.
The shorter 4.2 inlets may help a 4.5 make a bit more on top but probably at the expense of a bit in the middle. The net effect in terms of area under the curve will be pretty much nothing so it really depends on how you use the car. If you wring its neck regularly then 4.2 inlets are the way otherwise stick with 4.5s. This is why people have such success with the shorter inlet pipes fitted to 4.5 inlets. I have a set fitted and they do help right at the top but IMHO it's just the headline figure that improves, again, fine if you drive it at the absolute top of the RPM range a lot otherwise it's no more than pub bragging points.

Significant power gains require a bit more than the bolt on power boosters, most notably the standard exhaust manifolds are a bit crap and a few companies have made some that should be worth a few BHP. The MBE ECU can be improved on too, or to be fair, it's map can be improved. The top power producers have gone a lot further than bolt on kits to get where they are and take my word for it that the only way to compare them is on the same dyno on the same day as dyno operators are not in the business of offending paying customers. Some of the dyno shootouts in the forum can give a good idea of what works and what does not but you need to see the curves not just the peak BHP number to get a real idea. 2" long throttle bodies bolted straight to the head will give an impressive BHP number but a totally undriveable car with useable torque spread of a couple of thousand RPM at or beyond the redline.

Sorry, I tend to go on a bit..