TeamRX8

iTrader: (2)

one factor is it was only 60% TPS at the emap crossover point, looks like you didn’t really roll into until the last 500 rpm or so
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Vicoor

Howard,
Since this thread I've been thinking about the method of measuring exhaust manifold pressure.

I am having doubts about the effectiveness of measuring via a port in the manifold runner or at the entrance to the turbo.

Bernoulli's principle states that as velocity increases, static pressure drops.

Measuring static pressure anywhere inside the manifold would be totally influenced by the velocity of the exhaust stream.

I'm thinking the best place to measure may be the EGR port.

Slides

Isn't that just adding a different volume whose entrance is still referenced to a more energetically pulsing flow stream?


I'd agree than any comparison in intake to exhaust manifold pressure above about 2500rpm is meaningless unless you are very near 100% throttle, there could have been a significant pressure drop across the throttle at those revs which requires more turbine energy (and thus pressure to drive). Do you have wastegate position sensors? Would be easy enough to do back to back runs to compare.


Edit: predictive text is a PITA.

j9fd3s

iTrader: (3)

or the ACV port. the ACV would give you an average of both ports, not sure about the EGR. it may not matter, and the EGR is easier to get to on the FD

AlexG13B

iTrader: (7)

I'm running my emap thru acv block off plate. seems to be reading ok I suppose . was curious if anyone ever compared that reading to reading in manifold

TeamRX8

iTrader: (2)

why would it be any different at all?

it may be static there, but it’s not static at the source opening, which it will only reflect the pressure from that point.

seems to be a hair splitting exercise because the magnitude difference is likely being given more weight than it deserves.
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Vicoor

My thought is that when measuring static pressure in a high velocity stream, such as a turbo manifold runner, the data collected may be as heavily influenced by the location of the measurement as the design of the manifold.

By measuring as close to the inside of the rotor housing as possible you may get a much more accurate representation of the "backpressure" the engine sees and therefore a better picture of how a particular turbo system (turbocharger, manifold, wastegate, and exhaust system) performs.

TeamRX8

iTrader: (2)

I was referring to the ACV vs EGR port part of the conversation, but I’m still of the opinion it may be given more weight than deserved. It’s not even constant, but cycles when you get down to it.

There’s velocity coming through the throttle body as well and right behind it is considered the optimum measurement point for the MAP sensor. Should there be concern about the accuracy of it too?

TeamRX8

iTrader: (2)

A G30-770 from ATP will be arriving here soon. This is a secondary project to my other RX8 and will likely be a bit before results are ready, but we’ll get there eventually.

I’m confident 66 lb/min @ 70% compressor efficiency and 30 lb/min turbine capacity @ 74% eff. is going to show that it's more than “good for 450 whp”. But let’s put aside referencing data/technology from over two decades ago and find out what’s really possible with where we are now instead …
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j9fd3s

iTrader: (3)

the ACV and EGR actually go to different places. the ACV goes to each exhaust port around the sleeves, so you'd get an average of that. the EGR just goes somewhere on the rear rotor
not sure what difference that would make if any, i'm sure someone thought of it before, but it didn't really occur to us until about a year ago.

boringly, the US/EU 93-94 intakes are the only ones with EGR, although the engine seems to have that port all the time





JDM intake for comparison

TeamRX8

iTrader: (2)

I can’t say for sure, but am questioning whether it matters wrt being any more accurate for the reason stated. There are other threads on the forum stating at the turbo entrance is more accurate. Pretty much just like anything else, such as using 2” Sch. 10 vs 1.5” Sch. 40 for the turbo piping and hundreds of other things we go on about.

j9fd3s

iTrader: (3)

agreed, either one is probably accurate enough. just pointing out that there is a physical difference.

AlexG13B

iTrader: (7)

I'm running mine from acv too ffe canister kit. have only take a log or 2 on my setup.
IRP manifold with 8374 IWG
from what I saw so far (albeit brief) emap seemed to be mostly lower then imap. I did notice at one point though at start of boost emap actually showed pressure before for imap for an instance before imap took over

Howard Coleman

iTrader: (6)

"one factor is it was only 60% TPS at the emap crossover point, looks like you didn’t really roll into until the last 500 rpm or so"

finally had a chance to do another run.

i was able to go 100% TPS at 5200 and hold it as opposed to a choppy throttle in post 50.

choppy throttle crossover (emap/emp = to boost) was at 5687

crossover today with full throttle was at 5774

both were at 20 psi.

i had to end my run today at 6357 boost 20.0 backpressure 23.7

choppy throttle run at 6357 boost 20 backpressure 24.9

it doesn't appear throttle position effected crossover or backpressure.

i look forward to posting some higher rpm and boost numbers.

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