435hp through standard 4.2 intakes
Discussion
Had late night at Austec with Paul and Tom tonight, just finishing off the car ready for Fighting Torque. Hit major snags with the modified 4.2 intakes playing up and unable to set the car up to run smoothly and to Pauls liking 
. So we reverted to a completely standard set of 4.2 intakes, albeit with different injectors which actually have a slightly lower flow rate that the standard ones but have a better/finer spray pattern.
I'm glad to say all was not lost
it still managed to suck 435hp through the restrictive intakes and produce 393lbs of torque to boot and put a smidgen under 360hp at the wheels where it counts :thumbsup:.
Those observant of you will notice a bit of a dip just under 3k rpm, we had to take the map back at this point as it appears the airbox/intakes were hitting a resonance which was causing shunting and not the usual smoothness. Also the wheel figure hits a plateau at 5k5 rpm from whihc point the standard intakes were not giving much more air for the car to breath
. So we reverted to a completely standard set of 4.2 intakes, albeit with different injectors which actually have a slightly lower flow rate that the standard ones but have a better/finer spray pattern.I'm glad to say all was not lost
it still managed to suck 435hp through the restrictive intakes and produce 393lbs of torque to boot and put a smidgen under 360hp at the wheels where it counts :thumbsup:.Those observant of you will notice a bit of a dip just under 3k rpm, we had to take the map back at this point as it appears the airbox/intakes were hitting a resonance which was causing shunting and not the usual smoothness. Also the wheel figure hits a plateau at 5k5 rpm from whihc point the standard intakes were not giving much more air for the car to breath
Was talking to APM about 4.5 running through 4.2 inlets as I think this is what they are doing with JohnnyW's Racer, said he hasn't had it on the rollers but is certainly punchy. Is there theoretically a benefit to the 4.2 system (once modified to allow more flow) over the short induction that a lot of people fit to the 4.5 system, i.e. is there a reason you have not just gone for the latter. Scuse the question from a mechanical numpty but trying to learn a bit here as might be rebuilding next year and want to gen up a bit 
The 4.2 intakes are quite narrow compared to the horrible plastic tubes that the 4.5 has, but have a few good advantages.
Rigid sidewall to transfer the inlet pulse, injector after the butterfly, and of course they are shorter than the 4.5 thereby looking suspiciously like the whirlwind pipes
. One last advatage is that they don't flex when being bolted down to the inlets, so better setup on the throttle arms.
I have a 4.2 set of inlets and would be quite prepared to put them on my 4.5 instead of my current pipes but for one reason.
I can't for the life of me see how to accurately machine a bigger diameter round the curve of the pipe without busting them, and considering I sepnt a lot of time getting a few thou out of my current inlets, losing 5mm seems a big hill to travel down for all those advantages.
Rigid sidewall to transfer the inlet pulse, injector after the butterfly, and of course they are shorter than the 4.5 thereby looking suspiciously like the whirlwind pipes
. One last advatage is that they don't flex when being bolted down to the inlets, so better setup on the throttle arms.I have a 4.2 set of inlets and would be quite prepared to put them on my 4.5 instead of my current pipes but for one reason.
I can't for the life of me see how to accurately machine a bigger diameter round the curve of the pipe without busting them, and considering I sepnt a lot of time getting a few thou out of my current inlets, losing 5mm seems a big hill to travel down for all those advantages.
Steve_T said:
I think you may be worrying about nothing tbh Julian. Harry's engine is making good power and Andy at APM has chosen a similar approach to JohnnyW's race car. I doubt that's coincidence.
I could be wrong but I think harrys car has been increased in capacity. In other words he has a much stronger air pump than me. His car could suck a golfball through a straw. Although restricted he is still getting more power from the increased capacity.On the other hand I rekcon the graph shows he is restricting air at the top of his graph.
He, like me, has the potential for more power from what that graph is saying, if he stops restricting. Without increasing my capacity my options are removing the restriction.
Of course I could be wrong and harry's car is competely standard capacity at which point call me eggy face
HarryW said:
'Eggy face' mine is 4525cc yours is 4475cc, all of 50cc
Don't knock 50cc, I used to have a garrelli moped that could do 45mph based on them 50ccs .I am surprised though that you seem to be demonstrating that the standard 4.2 inlets are good for 430bhp on a standard 4.5.
What bit of the puzzle am I missing?
julian64 said:
I have a 4.2 set of inlets and would be quite prepared to put them on my 4.5 instead of my current pipes but for one reason.
I can't for the life of me see how to accurately machine a bigger diameter round the curve of the pipe without busting them, and considering I sepnt a lot of time getting a few thou out of my current inlets, losing 5mm seems a big hill to travel down for all those advantages.
thinking about sending mine to these guys one dayI can't for the life of me see how to accurately machine a bigger diameter round the curve of the pipe without busting them, and considering I sepnt a lot of time getting a few thou out of my current inlets, losing 5mm seems a big hill to travel down for all those advantages.
http://www.extrudehone.com/afmpro.html
brummiewedge said:
How much power did you start with? 435bhp sounds respectable, not much more for the 100bhp per litre figure, not many 2 valve motors can achieve that (if any).
I race a stroked, 2-valve, pushrod Chevy V8 on a carb with 100bhp/litre ...7 litres of it.Good result Harry.
jeremyc said:
julian64 said:
I am surprised though that you seem to be demonstrating that the standard 4.2 inlets are good for 430bhp on a standard 4.5.
What bit of the puzzle am I missing?
Different cams perhaps? I'm sure Harry will be along to enlighten soon .... What bit of the puzzle am I missing?
.What is not apparent for the graph/figures was the map was specifically made to be ultra safe for Fighting Torque where sustained high revs are to be expected i.e. it is very much on the rich side, much nearer lambda 0.8 than 0.9 so is in itself knocking a bit off.
If it was headlines only then it could have quiet easily have been made to hit 440/400 last night
. However I'll save the headline bits for when the modified intakes are re-worked and tried again, I'll start a sweep stake as to where its going to end up.HarryW said:
jeremyc said:
julian64 said:
I am surprised though that you seem to be demonstrating that the standard 4.2 inlets are good for 430bhp on a standard 4.5.
What bit of the puzzle am I missing?
Different cams perhaps? I'm sure Harry will be along to enlighten soon .... What bit of the puzzle am I missing?
.What is not apparent for the graph/figures was the map was specifically made to be ultra safe for Fighting Torque where sustained high revs are to be expected i.e. it is very much on the rich side, much nearer lambda 0.8 than 0.9 so is in itself knocking a bit off.
If it was headlines only then it could have quiet easily have been made to hit 440/400 last night
. However I'll save the headline bits for when the modified intakes are re-worked and tried again, I'll start a sweep stake as to where its going to end up.julian64 said:
HarryW said:
jeremyc said:
julian64 said:
I am surprised though that you seem to be demonstrating that the standard 4.2 inlets are good for 430bhp on a standard 4.5.
What bit of the puzzle am I missing?
Different cams perhaps? I'm sure Harry will be along to enlighten soon .... What bit of the puzzle am I missing?
.What is not apparent for the graph/figures was the map was specifically made to be ultra safe for Fighting Torque where sustained high revs are to be expected i.e. it is very much on the rich side, much nearer lambda 0.8 than 0.9 so is in itself knocking a bit off.
If it was headlines only then it could have quiet easily have been made to hit 440/400 last night
. However I'll save the headline bits for when the modified intakes are re-worked and tried again, I'll start a sweep stake as to where its going to end up.Oh forgot to mention with the chnage bck to standard intakes I didn't get to fit the pulse plates so there is a little more to bolster that Torque up.
Re teh 100hp/ltr I actually think the Torque at 393lbs @ 5k3rpm is more impressive
and considering it should have peak torque at 5k5-5k7rpm it indicates more air will allow the peak to raise and hang on to. touching cloth said:
Was talking to APM about 4.5 running through 4.2 inlets as I think this is what they are doing with JohnnyW's Racer, said he hasn't had it on the rollers but is certainly punchy. Is there theoretically a benefit to the 4.2 system (once modified to allow more flow) over the short induction that a lot of people fit to the 4.5 system, i.e. is there a reason you have not just gone for the latter. Scuse the question from a mechanical numpty but trying to learn a bit here as might be rebuilding next year and want to gen up a bit
Just picked out the question the middle of your post TC .Main advantage of the 4.2's as I understand it is the injector sprays onto the back of the inlet valve instead of onto the back of the throttle butterfly. You could also make a case for the throttle assembly as a whole being better quality/design on a 4.2 too.
Andy at APM knows a thing or two about cerbs and as already pointed out earlier he has chosen this route for his (JonnyW's) race car
RR is about 11.5:1 I beleive I'm around 12:1
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