4.2 Intakes

[Julian64]

Thanks muchly to Longbow, and TT Tim for delivery, I now have a set of 4.2 Intakes for my 4.5 to experiment with.

I must say it seems obvious to me that the 4.2 system is far superior to the 4.5 system for design and probably fell down for simple monitery costs of production, as I can't believe the purple pipes were superior in any way.

But I was just looking at the intakes and wondering if anyone has done the measurements to prove any difference in air flow rate?

[HarryW]

agree they are superior in design particularly with the injectors being downstream of the butterflys.
I haven't got the data yet but I have a set that have been bored out where possible and will have back to back results from the engine Dyno on them compared to standard 4.2/standard 4.5/modified 4.5.

I think you will find the Boss Cerb runs a 4.2 arrangement with racer airboxes and gets 505bhp/440lbs out of them, so they can't be all bad.

[trackcar]

They are certainly restrictive .. just some basic work that i used to do in them released 12-15hp at the top end and that's before we had remapping so that's without any mixture or timing map changes, just pure airflow increase.

[Julian64]

Any chance of sharing what the basic work consists of? Or are you going to be enigmatic

Fair amount of meat on the pipes not sure how the stock diameter compares to the purple pipes.

I was staring at them and thinking how is it that sequential injection is of no benefit. Surely its better to have an atomised spray than suck the liquid fuel off the back of the valve each time.

Maybe the valve is hot enough to form a fuel vapour

[trackcar]

yeh once you get them cleaned up inside get your finger stuck in there and feel the changes in surface, there's some sharp machining edges and also a fuel "trip" at the end of the manifold where it bolts to the head face designed to reintroduce any wall-wetting fuel back into the airstream .. get rid of it all .. then just thin the non-threaded side of the spindle on each butterfly and hey presto instant hp. well when i say instant i mean after about 4 hours of carbide cutter work lol ..

after all that you'll be up to the flow rate of the std 4.5 inlet system but with a much snappier throttle but slightly less hp below 3k revs (going on what we know about the long v short inlet lengths and the ouright hp capability of the 4.2 v 4.5 versions*)


caveat : not withstanding the numbers to come off harry's engine yet but that engine isn't std.

[Julian64]

Thank Jules, any work been done on thinning the walls, or changing the trumpet length, cos from what I measure its about an inch short of utilising the pulse wave at 4K?

[trackcar]

Have never touched anything else in there other than basic smoothing really .. but if you think there's mileage in it be my guest welcome to the world of cerbera development.

Also i see no reason why a remapped and inlet-ported 4.2 shouldn't make the 380+ that we see from 4.5s .. they just need a better exhaust system

Are you planning to use them on your 4.5 then Julian?

[Julian64]

Hole in one. Can't think of a reason why not. The purple hoses don't seem a very clever idea to me. The throttle mechanism on the 4.2 intake also looks like a step up. But more than anything else watching the fuel piddle onto the butterfly in the current system looks terrible. I want a decent injector with a flower head spray pattern aiming directly at the inlet valve. And I want an inlet track that doesn't flex. I want a higher pressure of fuel in the fuel gantry and the injector mapping times reduced and moved to the inlet time, obviously preferably sequential or not a lot of point. And I want to do it all myself.

Then I'll be happy even if the car produces less BHP.

Out of interest do you know if the crankshaft sensor pulse to the ECU actually corresponds to TDC or some variation?

[trackcar]

Julian YHM or will do just as soon as I type it

[Julian64]

Thank Jules, That clears up my pulse problems from the crankshaft sensor to the ECU, although strangely my findings weren't strictly the same as either of yours, but it may be my system of measuring.

Cheers, gives me some food for thought