Intake runner diameter

[jeffro ra28]

I would say that a modification to a inlet runner that induces detonation is detrimental to engine performance .

We could say that you have actually increased the dynamic compression ratio by improving cylinder filling hence the result of some pinging? and the need for retardation of ignition timing.......

Chuck it on the dyno

[abently]

Sorry to burst your bubble but it would be pinging from even worse cylinder to cylinder flow distribution then Factory. The MAS can easily compensate for a reasonable increase in air intake...

But hey what do I know.... lol

[amichie]

But hey what do I know.... lol

He I'm wrong 99.9% of time. Just ask my wife.

[jeffro ra28]

But hey what do I know.... lol

Why dont you try telling us how much you know rather just talking shit?

Tell us why it may be pinging perhaps? I think OC said it when he suggested that you just sit back and handwave at things without presenting any specifics on the matter.
Im sure most of us are open to discussing. Try approaching things in that manner and you may not sound like such a dick all the time.

[oldcorollas]

MAF will sense the increased airflow if VE is increased.

MAF signal goes up, ie LOAD sensed increases (for a given RPM)
when this occurs, the ECU will pull timing out.

it will ping if the ECU is not pulling enough timing. on a stock ECU that is quite possible.

is AB actually KM?

seriously tho Abently, it would be great if you try to explain your ideas more.
you and everyone else would get a lot more out of your posts if you did

Sorry to burst your bubble but it would be pinging from even worse cylinder to cylinder flow distribution then Factory. The MAS can easily compensate for a reasonable increase in air intake... You really should setup the venturi's in the manifold on a flow bench or at least weld in bungs on each primary to fix each individual venturi's position in relation to the AFR results under dynamic conditions.

Why are you confident that reducing port diameter will make air distribution in the manifold worse? can you explain why you can say that?

as you should know, flowbench does not replicate dynamic conditions...
but the point of original post is that he is trying to FIX the problems... make it BETTER
i assume that would start from changing the runners to the correct diameter for best VE 8partly theoretical), and THEN fix the manifold for distribution or do away with plenum altogether.

to set up venturies(?) to try to compensate or make the best of a crap manifold is arsebackwards....

[amichie]

Here is another way of looking at this issue.

The 7m-ge has approx 32 % more port cross sectional area than the small port 4age.

The capcity of each of the 7mge cylinders are 25 % larger than the 4age.

The smallport 4age without the TVIS system has peak torque at approx 6000rpm and peak power above 7000rpm.

The 7mge intake area is tuned for approx 5% higher rpm than this. I would much prefer to have ports tuned for say peak torque at 4500rpm and peak power at 5500rpm and let the computer change gears at 600rpm just as you roll past pek power.

The venturis were an experiment and the next step would be to properly modify the head and manifold so that the cross section tapers down smoothly.

Can anybody recommend some suitable epoxy fo filling aluminium heads and manifolds.


BTW I highly recommend this web site for porting tips. It's not commercial and Guy has considerable experience including in formula 1 engine design.

I only looked it up searching for the port dimensions of the FIAT LANCIA 2L DOHC that I clearly remember had heaps of torque throughout the rev range and Guy is the FIAT guru.

http://www.guy-croft.com/

[jeffro ra28]

As for epoxy i have succesfully used, "Z-spar" sourced from Performance Wholesale, or "Epirez", from blackwoods.
There is other stuff made by ITW polymers in the states which is used for boat hull repairs. This is probably better then both those products but is hard to get. A prostock cylinder head porter i used to associate with put me onto this. He used to send me samples, and actually used it himself. Do some web searching and you may find it. Customs loves to punch holes in the tins tho

The key properties you are looking for are heat expansion similar to aluminium, resistance to petrolium and vibration

EDIT: i had a good look at some porting articles on guys website. He explains exactly what i tried to above. Divergence is the word i think he used . That is in regards to your port restrictor

[amichie]

As for epoxy i have succesfully used, "Z-spar" sourced from Performance Wholesale, or "Epirez", from blackwoods.
There is other stuff made by ITW polymers in the states which is used for boat hull repairs. This is probably better then both those products but is hard to get. A prostock cylinder head porter i used to associate with put me onto this. He used to send me samples, and actually used it himself. Do some web searching and you may find it. Customs loves to punch holes in the tins tho

The key properties you are looking for are heat expansion similar to aluminium, resistance to petrolium and vibration

EDIT: i had a good look at some porting articles on guys website. He explains exactly what i tried to above. Divergence is the word i think he used . That is in regards to your port restrictor

What about JB weld?

I like Guy Croft's web site because it a great resource for NA engines.
But it does lack the vibrant and rapid discussions we have here on Toymods.

[jeffro ra28]

Never used it.....
Z-spar is actually a product designed for cylinder head ports

[Sam_Q]

what about Q-bond? would that hold up?

[amichie]

Here is a good read on intake port sizing. Scroll down to the section on 4 valve heads.
This guy also claims a lot of 4 valve engines have intake ports that are way too big.

http://www.gofastnews.com/board/tech...ort-areas.html

[Sam_Q]

thats a pretty decent read

[abently]

Here is a good read on intake port sizing. Scroll down to the section on 4 valve heads.
This guy also claims a lot of 4 valve engines have intake ports that are way too big.

http://www.gofastnews.com/board/tech...ort-areas.html

Yes, he's referring to 4 valve Heads that were made back some 30+ years ago in the good ol U S of A........ you know the same place where some still believe 2 valve Heads are somehow superior to 4 Valve Heads... lol.

The only reason intake runner diameters were larger on the Euro/Asian 4v vehicles 20 years ago then they are now is all to do with the port/valve angles as there is a max / optimal speed before the fuel/air mixture no longer remains uniform as it travels around a SSR. Ports now days are on the extreme end of being vertical (i.e. no SSR, no radius of any kind from the Injector location to the Valve seat) and this is why higher port speeds (ie. smaller runner diameters) are possible.

[LeeRoy]

Yes, he's referring to 4 valve Heads that were made back some 30+ years ago in the good ol U S of A........ you know the same place where some still believe 2 valve Heads are somehow superior to 4 Valve Heads... lol.

Your not entirely correct. At a high enough power output 4 valve heads become inferior.

[Sam_Q]

with nitromethane?