Pigeons & Valves :P

MkngStffAwesome

MkngStffAwesome

Active member
So this is about Compressor surge (Pigeon) and Blow of valves.

I think there should be a clear distinction in this thread between if you NEED one and if you WANT one.

For the total COOL factor id love to get my car to pigeon...

Sadly for me i bought a anti surge housing which i think will stop the sound Pigeon.. I guess i could be another one.

I'm concerned about over boost with a that might happen with the Pigeon setup V Blow off..

Also because we probably wont be running a IC and all it's piping im not sure we could even get a decent Blowoff sound or pegion sound.

 
... if the blower is too big for your engine displacement you might end up with too much (constant) blow off ... not good.
It really is important to check the specific compressor map and do some calculations/math for the expected duty window.
You want the blow off only for the "borderline events". (which can be partially(?) eliminated with some smart eMotor control)

I am sure you know that ... but just a warning for the "beginner": bigger is not better in regards to compressor, despite independent rpm control of eMotor (not that simple, you want to stay in a good efficiency for the duty window, otherwise you will have disproportionate and counterproductive heat generation )
 
Last edited:
Surge is really nasty. I found that out when I still had the smaller SC impeller and volute; I tried running the e turbo with the engine off and the compressor pretty much immediately went into surge. I thought I broke something in my blower. It's really hard on the compressor (and therefore motor). A word of warning: my e turbo is really quiet. You can't actually hear it. Unlike the Whipple setup I built before it which sounded like, to use a phrase from someone off a mustang forum came up with, "a screeching velociraptor with the flames of hell licking it's ass:"


That was a good race - I WELDED that guy to the tree. Look at the reaction times on the slips.

Going back YEARS ago, when I was still running a tiny Eaton M90 on the car we were asked to participate in a full-size drag race shoot out. Here's the magazine article (we came in third, but first of the cars driven to the track): https://www.motortrend.com/events/0410mm-ford-muscle-car-comparison/

The author described driving the car (I let him make a pass) thusly: "...the cockpit sounds like you're riding under the wing of an F-14 Tomcat."

Anyway, back on topic - a blow off valve is a good idea - but you won't hear much, since the e turbo should be switched off (but spooling down) when the bypass opens; in practical use you'd have to manually activate an e turbo at the "wrong" time to get surge. Personally, I like not hearing the e turbo. That blower whine could get on your nerves after a while.
 
Back in the day there was nothing worse than compressor surge and people shuddered at the sound of it... However now it's the best sound your can make and many spend lots of money to let the pigeon out :)

The thing i mainly dislike about it is that surely at the time this must result in a huge boost back pressure in the inlet and if you re opened the throttle just before the sound (and probably during) it would result in a huge over boost condition.

Without motor braking ( Which is a bad idea due to the heating ) the motor will continue to spin just like a turbo and should need something to let the boost out.. so i would still think that a blow off would be a good idea... But from a sound point of view it probably wont be very loud cos there is such a small volume of air because there is no IC and piping everywhere to increase the volume to be bled off.

On to compressor efficiency i agree with what you said .. but at the same time assuming that it's not geared then going for a larger compressor enables you to get the boost at a rpm that an Electric motor can realistically achieve. Also a Big compressors will not create to much of a restriction when "OFF" which on a road car will realistically be 99.9% of the time probably.

In my case it's geared so there should be some gear noise when running.. this could be cool.. Im not sure how load it really would be though and if i could hear it over the rest of the car. i'll have to wait and see.


As for IC's i feel that should be a different topic entirely and i was going to start it yesterday because that is another topic that will be brought up.
 
MkngStffAwesome said:
Back in the day there was nothing worse than compressor surge and people shuddered at the sound of it... However now it's the best sound your can make and many spend lots of money to let the pigeon out :)

The thing i mainly dislike about it is that surely at the time this must result in a huge boost back pressure in the inlet and if you re opened the throttle just before the sound (and probably during) it would result in a huge over boost condition.

Without motor braking ( Which is a bad idea due to the heating ) the motor will continue to spin just like a turbo and should need something to let the boost out.. so i would still think that a blow off would be a good idea... But from a sound point of view it probably wont be very loud cos there is such a small volume of air because there is no IC and piping everywhere to increase the volume to be bled off.

On to compressor efficiency i agree with what you said .. but at the same time assuming that it's not geared then going for a larger compressor enables you to get the boost at a rpm that an Electric motor can realistically achieve. Also a Big compressors will not create to much of a restriction when "OFF" which on a road car will realistically be 99.9% of the time probably.

In my case it's geared so there should be some gear noise when running.. this could be cool.. Im not sure how load it really would be though and if i could hear it over the rest of the car. i'll have to wait and see.


As for IC's i feel that should be a different topic entirely and i was going to start it yesterday because that is another topic that will be brought up.
Click to expand...
btw ... the TP motors (the 5860 for sure and most likely the 5870 too) do not spin freely! You cannot even turn them by hand (seriously!).

So if in off position it is unlikely that the impeller will rotate just from the sucked in air (and we might have to look at the sweet spot under which the SC assembly really becomes a restriction and determine a part throttle/variable emotor rpm strategy).
Best would be a "by pass for off" tubing.
 
The motor and compressor will have inertia when you stop powering them so they well continue to spin.. obviously they will start to decelerate though.

Yeah you'd need a dyno to see how much restriction is imposed.. but really the dyno would need to be done at part throttle because at wider opening the SC will be running...

Im going with a part throttle low boost option.. actually boost will be based on RPM and Throttle pos .. and infinitely variable.. Partly because i feel like getting an instant hit of power will be horrible dangerous on the roads .. i dont have a LSD... in the rain ahahha.... boost kicking in part way around a corner .. ahahh
 
You must log in or register to reply here.
Top