What makes the extra power on tuned 4.5's?

[Duke Thrust]

Has anyone put the 4.5 induction set up on a 4.2 and had a re-map?

What else is different apart from the 300cc?

Curious you see

[ridds]

4.2 uses more aggressive cams I beleive, hence the noise.

Don't qote me on that though.

[simonsparrow]

Duke Thrust said:

Has anyone put the 4.5 induction set up on a 4.2 and had a re-map?

What else is different apart from the 300cc?

Curious you see

Good question. I understand that the later engines have larger main bearings on the crank, but I guess thats both 4.2 and 4.5.

I remember Trackcar saying that the 4.2 inlets were a bit small for big HP. Anyone tried aftermarket throttle bodies such as Jevney?

[trackcar]

the 2mm smaller diameter butterflies restrict the outright breathing on the 4.2 .. but it's shorter length is good for peak power at around 6000rpm, so it loses in one major respect to the 4.5 and gains in another (albeit smaller) way from it's shorter length.

A remapped 4.2 makes about 370bhp. a remapped 4.5 about 10-20 more.

I've just done a 4.5 today with short induction, linked decats and it's made 404bhp .. you'd never get that with a 4.2, it just doesn't have the airflow through the inlets.

[Duke Thrust]

trackcar said:

the 2mm smaller diameter butterflies restrict the outright breathing on the 4.2 .. but it's shorter length is good for peak power at around 6000rpm, so it loses in one major respect to the 4.5 and gains in another (albeit smaller) way from it's shorter length.

A remapped 4.2 makes about 370bhp. a remapped 4.5 about 10-20 more.

I've just done a 4.5 today with short induction, linked decats and it's made 404bhp .. you'd never get that with a 4.2, it just doesn't have the airflow through the inlets.

So what do you think is possible on a 4.2 with a 4.5 intake system (I'm assuming that it'd fit)

[Nickccc]

The question must be, "can the 4.5 tb's be fitted to the 4.2 to increase the flow?"

[nitro cerb]

There will be all new larger direct fit throttle bodies available for both 4.2 and 4.5 in the very near future!

Craig.

[Cyclone1]

nitro cerb said:

There will be all new larger direct fit throttle bodies available for both 4.2 and 4.5 in the very near future!

Craig.

That's more like it..........

[Duke Thrust]

nitro cerb said:

There will be all new larger direct fit throttle bodies available for both 4.2 and 4.5 in the very near future!

Craig.

Excellent!

[cerbfan]

Go on spill the beans, where will they be available from. Any price indications, what if anything else will need to be changed.

Looking forward to being able to get 400+BHP out of my 4.2!!

[trackcar]

bigger throttle bodies on the 4.2 are well worthwhile bigger on the 4.5 not worth anything at all ..

I have thinned the spindles down before now on the 4.5 inlets whilst chasing the magic numbers and adds bearly measurable increases for a considerable increase in x-sectional area and money spent, i've even run the 4.5 inlets with no butterflies and spindles aswell and still no real worthwhile increases (getting the thing to start and run on the rollers was a bit scary!) .. so the 4.5 inlets are well sized for 400(ish)bhp cars. I would imagine the bigger ones will work really well on some of the 5.0 and 5.5 litre engines with their ported heads though ..

Edited by trackcar on Tuesday 27th June 21:38

[nitro cerb]

trackcar said:

bigger throttle bodies on the 4.2 are well worthwhile bigger on the 4.5 not worth anything at all ..

What like when you said bigger exhausts wouldn't give more than 2-3 bhp!!!!!
But I suppose you'd know being the expert you are.

[ridds]

trackcar said:

bigger throttle bodies on the 4.2 are well worthwhile bigger on the 4.5 not worth anything at all ..

I have thinned the spindles down before now on the 4.5 inlets whilst chasing the magic numbers and adds bearly measurable increases for a considerable increase in x-sectional area and money spent, i've even run the 4.5 inlets with no butterflies and spindles aswell and still no real worthwhile increases (getting the thing to start and run on the rollers was a bit scary!) .. so the 4.5 inlets are well sized for 400(ish)bhp cars. I would imagine the bigger ones will work really well on some of the 5.0 and 5.5 litre engines with their ported heads though ..

Edited by trackcar on Tuesday 27th June 21:38

Quality, that takes balls. Doing that scares the shit outof me at work when I have full control of cylinder deactivation and on an engine dyno not a set of rolls!

[trackcar]

I did it by putting the full throttle fuel and ignition map all through the load sites so the fact the throttle pots weren't attached to the spindles didn't matter, then used the mapping box to trim the timing very retarded and the fuelling just weak enough to start and run, then on the dyno dynamics you can flick the load onto the rollers so whatever speed you start at it holds whilst you dial in the fuel and ignition really fast back to full strength .. then do the run .. you can then bring the roller speed back down again to a safe revs to switch the ignition off. I ran the scenario through my head for ages before I dared do it for real!

Edited by trackcar on Tuesday 27th June 22:46

[GreenV8S]

Is there a less traumatic way to do that just setting the rev limit to 2000 rpm?

Edited by GreenV8S on Wednesday 28th June 00:13

[BossCerbera]

trackcar said:

I've just done a 4.5 today with short induction, linked decats and it's made 404bhp ..

Can't wait to pick it up on Thursday!

[Cyclone1]

BossCerbera said:

trackcar said:

I've just done a 4.5 today with short induction, linked decats and it's made 404bhp ..

Can't wait to pick it up on Thursday!

Phil, I saw your Cerb at Track Car Solutions last week after it had had it's first run on the RR, and had a feeling it would make 400bhp+. Hopefully it'll now be snapping at the heels of your other monster.....the Boss Cerbera

Jules.

Edited by Cyclone1 on Wednesday 28th June 05:43

[Cyclone1]

nitro cerb said:

trackcar said:

bigger throttle bodies on the 4.2 are well worthwhile bigger on the 4.5 not worth anything at all ..

What like when you said bigger exhausts wouldn't give more than 2-3 bhp!!!!!
But I suppose you'd know being the expert you are.

Ironic that it was Joolz who advised me to go for the even "bigger" bore exhaust. Maybe it releases more potential on cars that are mapped as opposed to the std (340-360bhp) cars, via helping to release the greater volume of exhaust gases being created.

Jules.

ps......any chance of you posting up the spec of your rebuilt / modified engine, so that we can have a guess at what sort of power it is putting out prior to it's forthcoming rolling road run??

[trackcar]

nitro cerb said:

trackcar said:

bigger throttle bodies on the 4.2 are well worthwhile bigger on the 4.5 not worth anything at all ..

What like when you said bigger exhausts wouldn't give more than 2-3 bhp!!!!!
But I suppose you'd know being the expert you are.

..and they aren't worth anything on std cars which is where that came from .. the car making 404bhp is still on the std back box/intermediate pipes .. so it's not exactly short of flow is it? It's only now that we have cars consistently over 400bhp that other trends are starting to materialise. And it's only since we can take advantage of any pulse effects with a smooth exhaust that we can exploit finer and finer tweaks in the mapping to make full advantage of the smallest gains anywhere

I've *always* said that some cheapo aftermarket sports systems cost power .. and Cyclones car has one of those systems, it's a 4.2 set aswell so even smaller bore than the pucka 4.5 versions .. so his car was always a 420bhp car. It also means that the 420bhp quoted by TVR was only about 5% optimistic after all, assuming the early cars had big exhausts, and were correctly mapped .. which is a surprise but again only now that we can fully extract the info from the engines and mapping is the full picture emerging. You can only go on what you know at the time!

the trends are still:

std back box good for just over 400bhp.
corectly sized existing sports pipes systems behave same as above
cheap sports pipes appear to knock 10bhp ish off most of the rpm range ..a car capable of 420hp only makes 406/408hp in cyclone's case.

that's pretty much what i've always said.

I'd be very surpised if anything i've said about inlets turns out to be untrue. I'm not dissing any idas anyone else has, just giving the benefit of my experience on the thread .. I don't consider myself to be an expert .. just someone who does a LOT of testing, testing and more testing My cars always do what i claim for them, so I'd be inclined to think my testing proceedure is probably pretty sound

But good luck with your development, will look forward to seeing your car on the SRR dyno and the dragstrip

[nitro cerb]

trackcar said:

But good luck with your development, will look forward to seeing your car on the SRR dyno and the dragstrip

You'll never see my car at SRR but it will go on the drag strip some day. Mine isn't all about straight lines and never has been. I enjoy tracks far more and always will.