Chimaera 450 intake modifications
Discussion
Hi Guys,
Thought I would post the RR graphs from my recent upgrade work, for your reference and discussion…
I booked the Chimaera in to have a load of work done, including removing the stepper motor, lowering the idle speed etc. As part of the remapping work I was having done, I procured..:
44mm intake manifold
44mm thermal gasket
44mm plenum base
44mm aluminium flared trumpets
71mm plenum roof/butterfly
…to be fitted in place of the stock 38mm variants.
The car is reasonably modified for an NA car – existing relevant modifications include..:
ACT smoothbore intake & 90-elbow (all heat-wrapped)
AFM replaced with straight-thru pipe
TVR885 cam
TVR BV heads
S/S ex.manifolds (JE Engineering IIRC)
S/S Y-piece (with cat)
S/S swan neck
S/S exhaust
Emerald K6 ECU (fuelling and ignition)
The 38mm intake items were the last bottleneck within the system – so I was replacing these to enable the engine to breath better at higher revs.
The car has been mapped (both before and after) on 95ron fuel.
Here is the “Before” graph – note the BHP for reference on the next graph..:
Here is the “After” comparison graph, showing both before and after..:
I was kind of surprised by the results – to be honest, I expected..:
1. More of a gain – after all, 38mm must be a bottleneck at higher RPM
2. To lose torque at lower RPMs – it’s virtually identical
3. To have a reduced “max torque” figure… I actually appear to have gained some
4. The torque curve to move further up the RPM band than it has done (only about 300rpm)
My gut feel is that the cam doesn’t actually flow enough air in the higher RPMs to highlight the gain that the larger intake assembly can deliver – ie. the cam is actually the “bottleneck”, limiting the potential gains I might achieve at higher revs…
I think the cam is essentially good – I just wonder whether playing with the timing may yield larger gains if it allows more flow at higher RPMs (and therefore the new intake to “come into its own”)..?
Your thoughts gentlemen..?
Dom
Thought I would post the RR graphs from my recent upgrade work, for your reference and discussion…
I booked the Chimaera in to have a load of work done, including removing the stepper motor, lowering the idle speed etc. As part of the remapping work I was having done, I procured..:
44mm intake manifold
44mm thermal gasket
44mm plenum base
44mm aluminium flared trumpets
71mm plenum roof/butterfly
…to be fitted in place of the stock 38mm variants.
The car is reasonably modified for an NA car – existing relevant modifications include..:
ACT smoothbore intake & 90-elbow (all heat-wrapped)
AFM replaced with straight-thru pipe
TVR885 cam
TVR BV heads
S/S ex.manifolds (JE Engineering IIRC)
S/S Y-piece (with cat)
S/S swan neck
S/S exhaust
Emerald K6 ECU (fuelling and ignition)
The 38mm intake items were the last bottleneck within the system – so I was replacing these to enable the engine to breath better at higher revs.
The car has been mapped (both before and after) on 95ron fuel.
Here is the “Before” graph – note the BHP for reference on the next graph..:
Here is the “After” comparison graph, showing both before and after..:
I was kind of surprised by the results – to be honest, I expected..:
1. More of a gain – after all, 38mm must be a bottleneck at higher RPM
2. To lose torque at lower RPMs – it’s virtually identical
3. To have a reduced “max torque” figure… I actually appear to have gained some
4. The torque curve to move further up the RPM band than it has done (only about 300rpm)
My gut feel is that the cam doesn’t actually flow enough air in the higher RPMs to highlight the gain that the larger intake assembly can deliver – ie. the cam is actually the “bottleneck”, limiting the potential gains I might achieve at higher revs…
I think the cam is essentially good – I just wonder whether playing with the timing may yield larger gains if it allows more flow at higher RPMs (and therefore the new intake to “come into its own”)..?
Your thoughts gentlemen..?
Dom
Edited by domV8 on Thursday 17th March 14:19
I couldnt justify the extra cost on my extortionatley expensive engine rebuild.
The inlet side of things is low on the priorities for me tho.
Either something is amis or other builds are finding tricks that they arent sharing. We see a lot of 450's with these mods reaching the 320 to 340+ now.
Are you still running cats? Have the manifolds been port matched?
The inlet side of things is low on the priorities for me tho.
Either something is amis or other builds are finding tricks that they arent sharing. We see a lot of 450's with these mods reaching the 320 to 340+ now.
Are you still running cats? Have the manifolds been port matched?
dbv8 said:
I couldnt justify the extra cost on my extortionatley expensive engine rebuild.
The inlet side of things is low on the priorities for me tho.
Either something is amis or other builds are finding tricks that they arent sharing. We see a lot of 450's with these mods reaching the 320 to 340+ now.
Are you still running cats? Have the manifolds been port matched?
As mark Adams said, it's luck with these engines, look at my dyno and haircutmikes, nearly the same mods and 60 bhp in itThe inlet side of things is low on the priorities for me tho.
Either something is amis or other builds are finding tricks that they arent sharing. We see a lot of 450's with these mods reaching the 320 to 340+ now.
Are you still running cats? Have the manifolds been port matched?
My 450 made 273bhp NA with a few minor mods before the rebuild.
Maybe the proper rebuild with custom specced pistons will pay dividends.
The ported heads will add more but the bespoke nitrous friendly cam and low compression may take quite a few ponies away.
I am very interested to see the results after tuning and running in.
As long as it runs sweet, gives me comparable mpg and bhp to other 450's then i will be happy.
The fun will be had when i get to play with the good stuff.
Maybe the proper rebuild with custom specced pistons will pay dividends.
The ported heads will add more but the bespoke nitrous friendly cam and low compression may take quite a few ponies away.
I am very interested to see the results after tuning and running in.
As long as it runs sweet, gives me comparable mpg and bhp to other 450's then i will be happy.
The fun will be had when i get to play with the good stuff.
dbv8 said:
We see a lot of 450's with these mods reaching the 320 to 340+ now.
Are you still running cats? Have the manifolds been port matched?
ACT (JE?) Y-piece with 200-cell sports cat.Are you still running cats? Have the manifolds been port matched?
ACT (JE?) S/S manifolds with no pre-cats.
Fannymolds not port-matched by me...
Alexdaredevilz said:
look at my dyno and haircutmikes, nearly the same mods and 60 bhp in it
I have compared HairiCutMikes to all others - his is way in front. My £££ is on his high-compression pistons being responsible for that...Dom
Edited by domV8 on Thursday 17th March 15:56
I think he runs pistons without bowls (IIRC without looking)...?
Think for an NA engine, the compression can have a reasonable effect - up till the point that it becomes a problem in hot weather, or if using poor quality fuel etc...
However - I reckon that for us using standard pistons, playing with the cam (changing cam or cam timing) will have more of an effect on torque curves etc than anything else...
Dom
Think for an NA engine, the compression can have a reasonable effect - up till the point that it becomes a problem in hot weather, or if using poor quality fuel etc...
However - I reckon that for us using standard pistons, playing with the cam (changing cam or cam timing) will have more of an effect on torque curves etc than anything else...
Dom
My 4.6 griff made aroun 300brake in 2009.
Slightly raised CR, V8D Stg 3 heads, Kent 218 cam, I matched the inlet manifold to the heads myself and also opened it up to 45 mm to match the trumpet base.
Standard 64mm plenum so far, and an Emerald K3
Wonder what difference the 72mm plenum will make.....
Slightly raised CR, V8D Stg 3 heads, Kent 218 cam, I matched the inlet manifold to the heads myself and also opened it up to 45 mm to match the trumpet base.
Standard 64mm plenum so far, and an Emerald K3
Wonder what difference the 72mm plenum will make.....
to be honest dom there fairly respectable figures for a 4.6, sorry i was out on my 265bhp but i didnt realise what else you had done, you will get a few more ponies at the top if you retard the cam back 2-3 degrees, maybe see another 10bhp, but dont forget you will loose a the same in torque low down, the 885 cam isnt a revy cam and is never going to produce big bhp figures, but it was never intended for that purpose as far as i know, it was meant to cure the shunting problems and give a nice smooth power curve for general road use which in all fairness it kind of does, i fitted a one of my stealth cams to a customers car that wasnt very impressed with the shunting it caused, (although i still believe there where other issues involved somewhere) anyway we then fitted the 885 cam that he wanted and at the top end of the rev range the stealth made nearly 40 bhp more, however it also lost around 30ftlb at the lower rpm scale.
Ant. said:
My 4.6 griff made aroun 300brake in 2009.
Slightly raised CR, V8D Stg 3 heads, Kent 218 cam, I matched the inlet manifold to the heads myself and also opened it up to 45 mm to match the trumpet base.
Standard 64mm plenum so far, and an Emerald K3
Wonder what difference the 72mm plenum will make.....
If it were me, id buy a 80mm throttle body and get it welded on, im considering doing that my self soon, if you fancy going half's on the postage from the states? Slightly raised CR, V8D Stg 3 heads, Kent 218 cam, I matched the inlet manifold to the heads myself and also opened it up to 45 mm to match the trumpet base.
Standard 64mm plenum so far, and an Emerald K3
Wonder what difference the 72mm plenum will make.....
The 72 mm throttle bodie is going to gain you a couple of horsepower, an 80mm is going to gain no more, its more the shape of the plenum and air entry, if you weld the 80mm as high as you can on the plenum then you will gain more, dont forget all 8 cylinders dont suck at the same time!
v8 racing said:
to be honest dom there fairly respectable figures for a 4.6, sorry i was out on my 265bhp but i didnt realise what else you had done, you will get a few more ponies at the top if you retard the cam back 2-3 degrees, maybe see another 10bhp, but dont forget you will loose a the same in torque low down, the 885 cam isnt a revy cam and is never going to produce big bhp figures, but it was never intended for that purpose as far as i know, it was meant to cure the shunting problems and give a nice smooth power curve for general road use which in all fairness it kind of does, i fitted a one of my stealth cams to a customers car that wasnt very impressed with the shunting it caused, (although i still believe there where other issues involved somewhere) anyway we then fitted the 885 cam that he wanted and at the top end of the rev range the stealth made nearly 40 bhp more, however it also lost around 30ftlb at the lower rpm scale.
Yeah - it's a pretty good road cam I reckon.Just thinking that playing with the cam timing as you suggest, and mapping for 97ron rather than 95 would probably gain me somewhere between 10-20bhp for track days - without impacting the drivability too much...
Dom
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