4.2 Inlets to a 4.5

[Julian64]

Okay, hands up who's fitted a set of 4.2 inlets to a 4.5.

Anyone want to comment on what happened?

[HarryW]

Not got conclusive results yet, tbh but on mine so far the standard 4.2's seem to keep it to around 400, not that much effort has gone into improving the mapping to sort it.
However ported 4.2's may just be the ticket . In a short while I may be able to give you a definitive answer, if not the whole story.

[Julian64]

Not a lot of meat for porting on these beauties.

[HarryW]

Julian64 said:

Not a lot of meat for porting on these beauties.

tbh they are not that bad;
The butterflys are 44/45mm against 46mm for the 4.5's and you wouldn't notice too much difference on that, you can open them up to 46mm or slightly larger.
They have a much finer spindle diameter that doesn't really need profiling unlike the 4.5 lump of iron bar .
They have a much better quality spindle support/smoother operation.
They do have 'wasted' restrictions that can be cleaned out and then matching to the head.
Don't forget the pots are wired up differntly if trying on a 4.5 .
They give a much better throttle response, because al of teh above + the injector is downstream of the plate .

I know lots of hours have gone into making a set for my car which stand a chance of being junked if they don't measure up, if however when I say my car is complete with xxxhp/lbs and it still has the 4.2 bodies I'll be saying that for a reason .

Not forgetting the boss Cerb does have a similar arrangement to this, just need to get him to talk about his spec a little more openly, particularly now the factory has gone .

[trackcar]

HarryW said:

I know lots of hours have gone into making a set for my car which stand a chance of being junked if they don't measure up, if however when I say my car is complete with xxxhp/lbs and it still has the 4.2 bodies I'll be saying that for a reason .

LOL your engine is hardly a std 4.2 though harry .. if you suck harder you'll get more hp .. what i've always said is that the inlets are a restricting element in the 4.2 .. the engines aren't fundamentally different but the 4.2 ALWAYS loses out more than the bare capacity difference would have you believe, the inlets are the problem .. we know this because the ported inlets with no other mods (no mapping changes) gain about 12-15bhp! .. but you still can't get them to flow as much as a 4.5 system, iknow because i flowbenched the two when i first started doing what you're doing 4 years ago .. just make sure you get that straight and make sure you're comparing like with like with your big expose

[Julian64]

trackcar said:

HarryW said:

I know lots of hours have gone into making a set for my car which stand a chance of being junked if they don't measure up, if however when I say my car is complete with xxxhp/lbs and it still has the 4.2 bodies I'll be saying that for a reason .

LOL your engine is hardly a std 4.2 though harry .. if you suck harder you'll get more hp .. what i've always said is that the inlets are a restricting element in the 4.2 .. the engines aren't fundamentally different but the 4.2 ALWAYS loses out more than the bare capacity difference would have you believe, the inlets are the problem .. we know this because the ported inlets with no other mods (no mapping changes) gain about 12-15bhp! .. but you still can't get them to flow as much as a 4.5 system, iknow because i flowbenched the two when i first started doing what you're doing 4 years ago .. just make sure you get that straight and make sure you're comparing like with like with your big expose

So what part of this doesn't add up. 44-45mm with the 4.2 and 46 which compresses like a purple paperbag in the middle. Gives the impressed that the flow would be fairly similar.

What part of your flow testing was signalling the restriction?

[HarryW]

Joolz did you flow bench the standard 4.2 throttles, a set with the bottom ported out only and a set completely ported and larger butterflys fitted .

To port the bottom out gives gains for not a lot of effort on a 4.2 imho. To make it worth while fully porting them you have to have a bit more potential than a standard 4.2 lump under them though . I think my test will be comprehensive with back to back testing with the same engine with differing intakes, which is conclusive enough for me or anyone for that matter. Simple, if they don't make it inte the car then they didn't work, can't say fairer than that .
As mentioned in the other post it would be nice, if phil (boscerb) put some details up about the boss now the factory has gone under, the old secrets are TVR history .

[trackcar]

Fundamentally there are three sections which show up as problems on the flow bench .. what i call the fuel trip at the end of the manifold (the waisted section of machining) .. the steps into the main part of the manifold after the butterfly and the butterfly/throat size itself.

Even the 4.5 buterfly with thinned spindle is still holding back the airflow for the very highest hp cars .. we see this because you can keep thinning it down until you've taken one side away completely and profiled the other side and it keeps gaining airflow .. it's just on the limit at 385bhp and this is about what you get from a really well ported 4.2 set up on a remapped car (wheras a 4.5 in similar configuration would be making well over 405bhp) ..

all my highest hp cars (except cyclone's) had thinned spindles, cyclone's car never got that far but every other car i've thinned the spindle down on has gained hp. they are a restriction no matter what the bare sizing tells you.

In fact you can forget about the step-smoothing on the manifold joins that you see here on the forums (but it's sensible to do it if off the car for the mod).. if you have a cerbie producing over 400 genuine hp the best thing you can do for no money (only labour) is chop half the spindle away ...

[trackcar]

HarryW said:

Joolz did you flow bench the standard 4.2 throttles, a set with the bottom ported out only and a set completely ported and larger butterflys fitted .

To port the bottom out gives gains for not a lot of effort on a 4.2 imho. To make it worth while fully porting them you have to have a bit more potential than a standard 4.2 lump under them though . I think my test will be comprehensive with back to back testing with the same engine with differing intakes, which is conclusive enough for me or anyone for that matter. Simple, if they don't make it inte the car then they didn't work, can't say fairer than that .
As mentioned in the other post it would be nice, if phil (boscerb) put some details up about the boss now the factory has gone under, the old secrets are TVR history .

I only flowed the std 4.2s and fully worked 4.2s against the std 4.5s I've never fitted bigger butterflies to a 4.2, but if you take half the spindle away the gains are there so it implies the butterfly is still too small, and limiting the 4.2 below that of the 4.5 inlets. I would "expect" a 4.2 set-up with bigger butterflies and halfed spindles to be the highest flowing of everything except similarly reworked 4.5 versions but i say again i've never tested that configuration..

for driveability then the 4.2 system works best, but always loses out to the 4.5 in HP terms to the 4.5 set-up on std butterflies based on the evidnce from the rollers and what we know from the flowbench tests.

In hp terms the order would "probably" be:

half spindle 4.5s
half spindle 4.2s with larger butterflies
full spindle 4.5s
half spindle 4.2 fully ported std butterflies
std 4.2s

for driveability turn the list upside down

plus don't foget the 4.2s come with the benefit of an induction length more top end hp orientated than a std 4.5 induction until you run shorter pipes.

your test will be interesting indeed and i cant wait to see the results (and how well it goes at the pod) but won't tell us what the hp gains are on a std 4.2 by running the different systems .. which is i think what you were hinting at earlier as I'm the only person to stick my neck out about potential hp outputs from various inductions so far and i've been proved right most of the time so far mind you i don't believe some of the hp figures people are quoting from remapped 4.2s , 390bhp once!

So harry, what are you expecting from your beastie? we've heard claims of 440bhp from cerbies, and i have one that made 437 the other day .. so yours must be well over those for all the work ? 460? 470bhp??

[HarryW]

trackcar said:

HarryW said:

Joolz did you flow bench the standard 4.2 throttles, a set with the bottom ported out only and a set completely ported and larger butterflys fitted .

To port the bottom out gives gains for not a lot of effort on a 4.2 imho. To make it worth while fully porting them you have to have a bit more potential than a standard 4.2 lump under them though . I think my test will be comprehensive with back to back testing with the same engine with differing intakes, which is conclusive enough for me or anyone for that matter. Simple, if they don't make it inte the car then they didn't work, can't say fairer than that .
As mentioned in the other post it would be nice, if phil (boscerb) put some details up about the boss now the factory has gone under, the old secrets are TVR history .

I only flowed the std 4.2s and fully worked 4.2s against the std 4.5s I've never fitted bigger butterflies to a 4.2, but if you take half the spindle away the gains are there so it implies the butterfly is still too small, and limiting the 4.2 below that of the 4.5 inlets. I would "expect" a 4.2 set-up with bigger butterflies and halfed spindles to be the highest flowing of everything except similarly reworked 4.5 versions but i say again i've never tested that configuration..

for driveability then the 4.2 system works best, but always loses out to the 4.5 in HP terms to the 4.5 set-up on std butterflies based on the evidnce from the rollers and what we know from the flowbench tests.

In hp terms the order would "probably" be:

half spindle 4.5s
half spindle 4.2s with larger butterflies
full spindle 4.5s
half spindle 4.2 fully ported std butterflies
std 4.2s

for driveability turn the list upside down

plus don't foget the 4.2s come with the benefit of an induction length more top end hp orientated than a std 4.5 induction until you run shorter pipes.

your test will be interesting indeed and i cant wait to see the results (and how well it goes at the pod) but won't tell us what the hp gains are on a std 4.2 by running the different systems .. which is i think what you were hinting at earlier as I'm the only person to stick my neck out about potential hp outputs from various inductions so far and i've been proved right most of the time so far mind you i don't believe some of the hp figures people are quoting from remapped 4.2s , 390bhp once!

So harry, what are you expecting from your beastie? we've heard claims of 440bhp from cerbies, and i have one that made 437 the other day .. so yours must be well over those for all the work ? 460? 470bhp??

Nice clear and informative post Joolz Ta.
As to expected levels, you know as well as I do these can funny things to predict, I'll maintain that 430/380 is acceptable and is the lower target. If it gets north or 450 as it may do, but that's not certain, then all will be very good . If the torque is much over 380 i.e nearing 400 or over then I think that will be the bigger achievement.
I did say in one of my previous posts (not today but months ago) that I'm not actually chasing the out and out numbers as yes it could be made to give 470, but a balance between the two, driveablility and beastiness, then I'll have to take the driveabilty (and reliabilty) side of it .
The back to back test will also compare modified 4.5 arrangements up to a 48mm butterfly.
Re the 4.2 being the better length for power I think ideally you want it somewhere in between the 4.2 & 4.5 lengths tbh .

[spartacus]

trackcar said:

plus don't foget the 4.2s come with the benefit of an induction length more top end hp orientated than a std 4.5 induction until you run shorter pipes.

I may have misunderstood you here, but thought it was the opposite, i.e.. greater induction length = more top end, hence the cross-over purple pipes on the 4.5 cerbs which give longer induction length than the non cross-over 4.2 set-up. By the same token don't the AJP powered Tuscan racers have very short induction length to give more lower end grunt as top speed is not so crucial on a track car?

[HarryW]

spartacus said:

trackcar said:

plus don't foget the 4.2s come with the benefit of an induction length more top end hp orientated than a std 4.5 induction until you run shorter pipes.

I may have misunderstood you here, but thought it was the opposite, i.e.. greater induction length = more top end, hence the cross-over purple pipes on the 4.5 cerbs which give longer induction length than the non cross-over 4.2 set-up. By the same token don't the AJP powered Tuscan racers have very short induction length to give more lower end grunt as top speed is not so crucial on a track car?

The opposite is my understanding

[plasticman]

Are you sure about those butterfly dimensions , I measured some recently and made the 4.2 at 40mm and the 4.5 at 45mm. I was wondering if you could fit the 45mm butterflys into the 4.2 manifolds and decided it was probably impossible but have heard that a 43mm can be fitted ( with boring ofcourse)

[HarryW]

I physically sat (well stood next too) the engine builder a couple of weeks ago as I wasn't convinced either. He even got his digital ruler out (mic) . The ones that came out were definitely 44mm if not 45mm, I compared them directly to the 46mm standard 4.5 ones, got to admit I was surprised. Saying that even they look small compared to 48mm ones. I think the narrow throat and black paint gives the impression its a lots smaller than it actually is tbh. Re spare metal to open up, I think there's enough to smooth it out to a decent size that won't restrict the engine too much, if at all, but the dyno will tell.

[mars]

trackcar said:

all my highest hp cars (except cyclone's) had thinned spindles, cyclone's car never got that far but every other car i've thinned the spindle down on has gained hp. they are a restriction no matter what the bare sizing tells you.

And there lies the secret to my forthcoming poverty this year.

[Billy_rfc]

HarryW said:

I physically sat (well stood next too) the engine builder a couple of weeks ago as I wasn't convinced either. He even got his digital ruler out (mic) . The ones that came out were definitely 44mm if not 45mm, I compared them directly to the 46mm standard 4.5 ones, got to admit I was surprised. Saying that even they look small compared to 48mm ones. I think the narrow throat and black paint gives the impression its a lots smaller than it actually is tbh. Re spare metal to open up, I think there's enough to smooth it out to a decent size that won't restrict the engine too much, if at all, but the dyno will tell.

Any word on your project?

[HarryW]

Abroad again at the moment, so haven't really followed recent events, although I have saId to Paul he can still text me if he hits some good numbers .
Last strip down (the engine has been fully apart and back together more times than a Ho's draws ) was done a few weeks ago. Hopefully the last revision of piston design has gone in, fully coated ones now . Although there is a new 'engine man' at Austec now, who has injected a few additonal things to the last build . To be honest I'm surprised there hasn't been a bit of a press release with regards to him. Think big British hand built V8's that went into a British hand built car, some of which may have gone to France in balmy sumer June day's in years gone by, this man developed them .
Anyway back to throttle bodies, simple answer, I do not yet have the answer . I know Paul was trying to get it ready for saturdays Cerb RR day at Charlies, but teh rest of teh car i.e. suspension set up etc was going to have to follow on later, but I'm hoping to be rolling in early march and I wil tel all tehn .

Still not had an answer from Boss Cerb yet, his is making a claimed 500hp with (modified?) 4.2 intakes, although I think most of his gains are down to bespoke headers. Now that story could be much more interesting than mine.

[jensena]

HarryW said:

Abroad ................ Think big British hand built V8's that went into a British hand built car, some of which may have gone to France in balmy sumer June day's in years gone by, this man developed them ............

What Car !!! i'm racking my brains, I'll never be able to sleep if you don't tell us!!

[HarryW]

jensena said:

HarryW said:

Abroad ................ Think big British hand built V8's that went into a British hand built car, some of which may have gone to France in balmy sumer June day's in years gone by, this man developed them ............

What Car !!! i'm racking my brains, I'll never be able to sleep if you don't tell us!!

Well they weren't made of FRP I can vouch for that, think more bespoke hand rolled aluminium. The engine may have the man who built it name put on it too.

[cooky]

JJ?