funstick

Well define reversion ? there has never been any reversion ive seen. there is what we call sonic and turbulent airflow. seen plenty of that. and if the bend is close enough to the sensor you can create a eddy flow which will behave like reversion. as for engine reversion unless the maf is right up on the tb and youve got a flat exhuast cam lobe or a backfiring problem. Cant say ive ever seen an issue with it. and ive designed a few maf sensors so i think ive got some room to speak on the subject.

Trust me it doesnt happen. You could be reffering to wave dynamics. but yet again the incomming air mass is so heavy that its nearly 100% impossable for the plenum to breathe air back out. there is a slim chance you could be dealing with inertial wave action which would mimic engine reversion. but thats higly unlikely given the size of the air intake tubbing in terms of diameter and cubic volume and the short length of tubbing involved. it just seems very unlikely.

Bruce id think if youve had this phenomenon occur on the gn its most likely cuased by high FQ resonance waves bouncing from the turbo to the TB assebmly. the higher the static air pressure the higher the FQ. this could also create a phenomenon similar to reversion. Unless your maf ws really close to your turbo and you were getting the vortex affect of the plume of air exiting the scroll housing.

cant say reversion plays a factor. but these other phenomenon have pluaged maf desing for years.

Grumpy

Not on this.

Look at the fuel stand off, on any high rpm IR setup. All it takes is some observation to see. I picked IR, since it's easy to see in that application.

funstick

your not really seeing reversion. Its a phenomenon of fluid dynamics. Ever see the airflow pattern around the entrance to a turbo compressor scroll housing ? its hard to explian but it looks alot like a torodial electrical current. Its not reversion IE intake charge going out the throttlw opening. Its more like a colodial eddy current thats swirling in a turbulent manner at the opening of the air flow orrifice pulling fuel out with vacum. Note that most IR setups also have the injectors placed at or before the air inlet as well which of course contributes to the problem by providing fuel right at the center of the colodial eddy current.

Im not sure colodial is a good word to describe it but its been 14 hr day and im tired. ill see if i can find a few examples and scan them up out of some of my fluid dynamics text books.

ive observed the phenomeneon your talking about. but as i siad. the mass of air behnd the valve is so great IE atmospehre and the air in the runner its extremly unlikely unless youve got a mega tight lda like 104 on a early centeline that even in an ir setup that you would ever se reversion out into the air ducting. Thats alot of mass. i still think what youve observed are other phenomenon becuase in all the lab test etc as well as vehicles dynamics testing ive never able been once to recreate siad pehnomon at least not with any sort of conventional street engine that somebody here might be driving etc.

but if you put an elbow withing 6 inches of a maf boy does that cuase alot of ****. ask any ford engineer or hey call the guys who actually designed the maf eec iv system at prom m racing. they only hold alot of patents on maf sensors and would be glad to elighten you on the 1000's of hours theyve spent figureing this out.

Grumpy

What ever.

As for the 6"s and elbow, with a MAF yep, a real concern with the Ford's. GM has about negated that, with using the honeycombs, thou. I kind of doubt the ZO6 is much/if any longer then the 6"s and they don't even run a honeycomb.

The design approaches between Ford and GM tend to vary, alot.

Bjorn

Hello.

Sorry for nicking in to this post but I have a question.

When I go WOT I get 247 gr/sec at appr. 5200-5300rpm and it stays there up to 6000 (as far as i have pulled it). It feels as it just runs out of power around there 5300-ish, wery abruptly.

I read this post up and down and am a little confused....

In my case, is it just so that I run out of heads/cam etc. at this speed as a coincidence (SP??)or is it related to this 247 gr/sec?

I have a fresh 327 w. 224/236cam, victor jr efi, homeported 461:s 1.94/1.50 headers etc... and to stay w. the topic, descreened maf

thanks

/Björn

Twilightoptics

The maf only reads that high. What this means in your case is that you are at that gm/sec at that rpm. You still get more air coming into the engine, but you have to guess what gm/sec you are getting at those higher rpm. All you do is add more fuel in the PE vs RPM table in those higher rpm.

Get a wide band and see what your AFR is up there. It's the only way to not guess.