Gcg Turbo Specs

[chrissso]

After you give GCG your turbo and they machine out the turbine housing to a bigger exducer diameter, does this affect the A/R? Is it the same, or more?

Also, I searched GCG* for any date and got this below... (is the search working?)

I didn't find any specs on the GCG site.

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[R31Nismoid]

On thier website

EMAIL

Contact [email protected]

Surely if you wanted to know exact specs of something they would be more than happy to help?

[nissan_280zx]

aparently they keep the specs of their hi-flows well guarded, so none of their competitors can copy.

[paulr33]

i dont believe the a/r of the front or rear changes as it has the same housing and compressor cover on it. as far as i know + read;

new compressor wheel (flows more air)

new catridge

new bearing kit

bore out the exhaust hole

new exhaust wheel

i dont think they do anything with the exhaust housing, but they certianly do make the exhaust outlet larger and fit a larger steel wheel'd exhaust wheel to suit the larger opening

[Munna1]

i dont believe the a/r of the front or rear changes as it has the same housing and compressor cover on it. as far as i know + read;

new compressor wheel (flows more air)

new catridge

new bearing kit

bore out the exhaust hole

new exhaust wheel

i dont think they do anything with the exhaust housing, but they certianly do make the exhaust outlet larger and fit a larger steel wheel'd exhaust wheel to suit the larger opening

Paul they actually shave a heap out of the housings so the bigger wheels can fit and so they can flow more.

[paulr33]

ah cool, i was unaware. sweet

so they a/r would change ever so slightly then

[AlexCim]

they shave from the inside of the housings?

I thought they only bored out the holes to fit larger wheels.... at least thats all i could notice on my highflow.

[chrissso]

Well, I already looked at the web site and there was nothing.

I've emailed them this morning and will probably have to wait until Monday.

If they can't tell me a simple thing like what the new a/r is, then I might be convinced to go HKS.....

I searched for hi flow and got more results.

Found this:- (all results include supporting mods)

GCG hiflow is at 1 bar between 3200 to 3500 rpm. I would estimate that the a/r would be around .63 to.7 rwkw 220 to 260 with cam.

GTRS 1bar at 3500rmp a/r.64 rwkw 240 to 280 with cams, freaks hitting 300

2825 1 bar between 3500 and 3800 rwkw 250 to 300 cam. Deoending on A/r as well.

Most of these seem ot have a/r's around .6 to.65

Can anyone tell me more about where boost comes in and full boost with bigger a/r

Anyone know the a/r of the 300zx turbinehousing?

Thanks for any info.

[chrissso]

2825 should say 2835 - my bad...

[R31Nismoid]

front comp housing "really" doesnt affect stuff "that" much.

Its more the wheel/turbine thats responsible there and good matching between the two.

The comp housing is but a part of many that makeup the over-all spec.

So to single on this out isnt really the best way to do it

[AlexCim]

just because you cant find out the a/r you wont buy a turbo.

I bet there are hundreds of people on this forum using the GCG highflow and i bet all of us are happy (apart from that guy that put a GCG on his RB20...) with the turbo....

[chrissso]

I understand that there are many factors in turbo dynamics, but the main 2 that I want to know are compressor trim and turbine housing a/r. I understand also that GCG don't want to give away there secrets and dimensions of machining ect, but all I would like to know is the final a/r of the turbine housing after machining. I don't think that they should object to this. Anyway, I'll probably get a responce tomorrow.

Incidentaly, I wouldn't be put totaly off a GCG. They are easy to fit and there is good feedback on the forum. It's just that from the results, the nengun hks gtrs kit seems to be the sweet spot.

I noticed that the gcg hiflow has a 14 blade compressor. I was reading mafias thread about his upgrade and do remember someone (maybe discopotato) saying that the 12 blade is better suited. Anyone got anything more to back this up?

Thanks

[R31Nismoid]

Thats thread was about the GT30's though.

Using the t04s wheel or the GT40 wheel ... or something along those lines.

But they are totally different to the GCG

[discopotato03]

That 7/14 blade thing related to using 76mm TO4S compressor wheels with GT28 and GT30 turbines . You need to understand that the more blades/vanes a compressor has for a given diametre and trim the more air it tries to push at a given wheel speed . The more air it tries to push the greater the drive load it places on the turbine . Also GT series turbines (and compressors) are true high speed wheels and don't like having to lug wheels around that are designed to work at lower speeds eg TO4S compressors .

To turbine housings , you can't alter a housings area radius ratio by boring a larger hole through the housing . If you had a sectioned housing (across its axis not along it) you would see the volute curving around like a snail shell and the nozzle section which feeds the accelerating gasses into the turbine blades . When you fit the housing in a lathe and start boring you are removing material from the nozzle section rather than the volute so while the diametre is larger the volute is not . So the cross sectional area of the volute remains the same and the radius from the centre of the volutes passage to the centre of the housing remains the same - result no AR ratio change . What has happened is that the nozzle is now altered and often doesn't work as the designer intended . Also the larger diametre turbine probably needed a larger volute passage to pass the gas required to drive it with its native compressor in the turbo the turbine was designed to work with .

At the end of the day knowing what the AR ratio of the turbine housing is only helps you to know which direction to go if the one you have is not right ie too big go smaller and vise versa .

I believe Bretts Hi Flow works because the diametre of the turbine and compressor are closer than any Garrett GTBB turbo I know of and the trims are on the money for a responsive turbo . The wheels are also not worlds apart speed wise like a GT30/TO4S is so compliment each other rather than fighting each other .

I'm not going to blow the whissle on them and I'm only nearly certain what they actually are from looking at pics of them . Its enough to know that they are not super high tech or thermo nuclear protected but just a good combination that he managed to package in a cartridge and housings that are std to Skylines so go bolt with ALL the std fittings . Its handy that they can be tuned with a few different RB20/25/VG30 housings to suit different sized engines .

Compressor housing AR does make a difference which can be seen in the maps . With higher AR's the map islands grow wider meaning the surge lines are steeper and the wheels pumping efficiency increases in the lower pressure ratios . Note HKS often don't have comp housing AR numbers cast into them eg TO4Z and T51R , they are often a little larger than the similar sized Garrett to help avoid surge and pump more efficiently down low . The turbine housing will have more say in the speed of the turbo than the comp housing but then its up to the compressor size/trim /housing style and AR ratio to do the air pump thing .

[Munna1]

I understand that there are many factors in turbo dynamics, but the main 2 that I want to know are compressor trim and turbine housing a/r. I understand also that GCG don't want to give away there secrets and dimensions of machining ect, but all I would like to know is the final a/r of the turbine housing after machining. I don't think that they should object to this. Anyway, I'll probably get a responce tomorrow.

Incidentaly, I wouldn't be put totaly off a GCG. They are easy to fit and there is good feedback on the forum. It's just that from the results, the nengun hks gtrs kit seems to be the sweet spot.

I noticed that the gcg hiflow has a 14 blade compressor. I was reading mafias thread about his upgrade and do remember someone (maybe discopotato) saying that the 12 blade is better suited. Anyone got anything more to back this up?

Thanks

Yes, If I ever upgrade my turbo I will be buying the nengun GTRS kit if only I had the cash

[chrissso]

k. Thanks Guys.

Well I got an answer from GCG.

They say

"Chris, The A/r will be the same but the larger wheel will cause a little more Lag."

Which would indicate that they only bore out the outlet and not shave anything out of the inside of the housing.

[paulr33]

as i thought, thanks for confirming

[Sydneykid]

k. Thanks Guys.

Well I got an answer from GCG.

They say

"Chris, The A/r will be the same but the larger wheel will cause a little more Lag."

Which would indicate that they only bore out the outlet and not shave anything out of the inside of the housing.

Sorry I don't understand..............

GCG said the A/R doesn't change

Since A/R is a ratio they would have to machine out of the inside of the housing the same as they bore out the outlet, otherwise the A/R WILL change.

cheers

[paulr33]

the a/r ratio is the area of the snout/outlet to area of the compressor outlet? or am i confused? i remember looking at garrett diagrams but i still get confused

[Roy]

the a/r ratio is the area of the snout/outlet to area of the compressor outlet? or am i confused? i remember looking at garrett diagrams but i still get confused

Area/Radius. So if you take the cross sectional area at any point in the turbines scroll, and divide it by the radius you will end up with the same ratio, whatever that is.

So at the outer most part of the scroll you have the largest radius, so also the largest cross sectional area. Then as the scroll comes inwards the radius gets smaller, so in order toa maintain that ratio so does the corss sectional area. Hence the snail shape.

So if the turbine itself is bigger then the smallest R must be bigger....but do they actually modify the flute scroll etc of the exhaust housing....i assumed they just machined it out so the ratio of area to radius will always be the same...