Rimflow valves????
Turbo Mini Forums

Just about to start buying valves, springs etc for the cyclinder head and i was just wondering is there any benefit to using rimflow valves instead of the regular race inlet and exhaust valves minispares sells?

Hi,
They make a difference in a N/A engine if you're running a big cam, but some say not to use them on a turbo motor?
Cheers,
Gavin :)

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oh is that right! I knew that they were meant to be the best on an n/a motor but i did a search here and nobody had mentioned them........suppose that says it all really

I'm running Rimflow inlets in my head for no other reason than I've always used them in my N/A motors so carried on with them on my turbo. No idea if they work any better as I've not done any back to back tests!

they do work better in a na motor so work slightly better in a turbo, i used them for a few years but just use standard ones now with no side effects, plus they are a dam sight cheeper

always looking for them bigger bunches of bannanas

use minispares 214N Stainless race valves with the waist on them

they are hard to beat

I used to use rimflow inlets and mini spares stainless race exhust valves...before I went to the dark side!

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1/4mile in 13.2sec @ 111 terminal on 15psi

Wasnt the big thing about the Rimflows, the anti-reversion groove on the valve ?

Surely this should offer benefits on a turbo engine, as reversion is highly likely due to EGBP.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

If you pick the right turbo, then EGBP will be lower than boost and you will not get any reversion.

Hence, the Rimflow will not be beneficial.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

the aniti reversion groove was only on the intakes anyway,

this could be of benefit when the engines off boost.

the exhausts just had a nice big radius on the edge of the chamber side of the valve. chich would be easy enough to do to an ordinary valve.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

nope, but run it off a length of tube and you can considerable reduce the temperture. the response will not be as fast but still should be useable.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

the situation is that the inlet pressure is normally higher than the ebp , unitl a certain point in the rev band , thisa point is decided by how low you want the boost to come in ,and how efficiently everything is running , if you have the boost come in say 4k and max power is 5.5k then you could have a lower ebp ,but it would be a drag only car with a high converter . i have measured 30 psi ebp on a 20 psi inlet pr motor ,and was happy with that at max power .
to measure it paul , i used a brake fitting welded to the manifold ,and a 20 inch length of copper breake pipe in a coil and then a plastic hose on that to a guage ,worked perfectly , also you could do a run with the aux 3 on the inlet ,then another with it on the zorst ,and then overlay them in logworks ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

30:20 is still pretty damn good if you are getting a good wide useable power band from it.

Often it can be 2:1, or 3:1, or higher !!!! EGBP vs Boost.

As others say, its easy to measure.
Ive done it before. I welded a brake pipe fitting onto the manifold, and used a long spiraled bit of brake pipe to dissipate heat. Then just stuck a regular boost gauge onto the pipe.
Although you could drill/tap something into it too, and use a similar long pipe to dissipate heat.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

gosh i missed this q paul ,sorry , um no i dont go to excel , i load the graph for each sets of data then overlay from the menus at the top ,cant member which one ,then adjust base time to match.... you could also do the x y graph using rpm on the x line .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

OK, this is confusing.

How can the engine run this way? At the point where the intake valve opens, you'll have more pressure left inside the cylinder than in the intake manifold, and won't draw in any charge. The only way I can see it would work like this is if the exhaust pressure is quite spikey and you manage to blow down the cylinder far below the average (measured) exhaust pressure.

Not doubting the data, just looking for some info to stop my head spinning.

1275 with Back Door Turbo

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On 19th of Nov, 2007 at 09:01pm fortfun said:
OK, this is confusing.

How can the engine run this way? At the point where the intake valve opens, you'll have more pressure left inside the cylinder than in the intake manifold, and won't draw in any charge. The only way I can see it would work like this is if the exhaust pressure is quite spikey and you manage to blow down the cylinder far below the average (measured) exhaust pressure.

Not doubting the data, just looking for some info to stop my head spinning.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Which is why a lot of turbo applications do not like overlap.

However, get an efficient setup, boost:EGBP close to 1:1, then we can start to have overlap, and bigger cams which will allow more power.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

EGBP is the killer as we know
Hence my tailor made exhaust i run on my own mini

its hard to beat a N/A atmo cam above 260 deg what does the job right for road use

it would be nice to do a back to back test Steve on race valves and the rim flows on the same head ... with just the valves lapped in

Most peepes companies, have not the time and know what produces big power outputs in the 5 port head section

my guess is that there will be a slight benefit, But............ would the average chav basher recognise it ????

Right. Of course. Volumetric efficiency shot to heck for sure though as Paul noted.
Thanks - one more thing - at what sort of boost pressure have you guys observed the crossover? I'm presuming that when my wastegate opens at 8psi, I'm never getting close to 8psi back pressure.

1275 with Back Door Turbo

i gained 5hp on my na 1380 when running rimflows

always looking for them bigger bunches of bannanas