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The only difference in small vs large turbo is heat?

Pressure is pressure, so there is no more air volume with a big turbo.

My “small” 57mm old Garret was backed up by a huge ice water intercooler to fix the heat issue..

New “big” 57mm turbo should run a lot cooler, and the IC core is the same..

bug66 wrote: ↑Sun Oct 25, 2020 8:43 am The only difference in small vs large turbo is heat?

Pressure is pressure, so there is no more air volume with a big turbo.

Euh... no and...no (sorry)


This is also in reply of previous question/remark by Ruben regarding the benefits of a bigger turbo:
- a big turbo is much more kind for the engine as boost at low RPM (small turbo's) is much harder on engines and gearboxes.
- 25psi seems the same as 25psi, but from the engine's point of view (the topic we discussed) its not really: the difference of course being backpressure! Small turbo's usually have smaller turbine housing, so the same 25psi with 25 psi backpressure of 50 psi backpressure (yes, you have those) makes all the difference! Thats also where the extra 'heat' is coming from in those two examples. High back pressure gives more heat on your exhaust valves, deliveres LESS horsepower and raises temps in general. Yes, you get a bit quicker spool, but not all aircooled engines can take that..

In summery, you forgot the turbine side in all this.
Imho turbine side may even be more impotant then compressor side, which we usually focus the most on. Thats also part why I love Borg Warner airresearch turbo's over Garrets: Garrets always have (had) relatively small turbine wheels and they are only just recently - with their new line of turbo's -'catching up' on BW in that aspect. Thats a huge part of the the physical reason why your new BW will run cooler then your same (compressor)sized old Garret and make more power at the same boost.
But...thats all just my opinion of course .

I'm not a pro in that kind of knowledge. It was just a logical assumption.

(At least in my head it sounded logic)



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Yes, I was talking about the intake side. 97.2% of us just measure that pressure side..

Back pressure and strain on the engine “from that side” is of course a whole new side of the boost coin.

I think I'm going to put a sensor on each side and log some measurements.
And maybe a temp sensor before the intercooler too so i have that data as well.

I added a pre intercooler bung for IAT. Just to see how effective the double chinese intercooler is.

Should probably also do a back pressure gauge.

Back pressure sensor would be interesting.

Mag case 4 studs per cylinder[normal "thin wall" 94mm cylinders] & regular UK available petrol max 26psi with water to air intercooler in my 1303 road car, yes it could probably go higher but it is already just about undrivable on full boost on normal roads!!!
The other street car has seen well into 40psi range on track with better fuel

bug66 wrote: ↑Thu Oct 22, 2020 3:00 pm My 2165cc made 501whp on 32psi.

Aluminium case. 4x10mm studs per cylinder.

No fancy stuff.


32psi is not that much...

If it really made that much then why is it so slow?

buguy wrote: ↑Mon Oct 26, 2020 1:47 pm I think I'm going to put a sensor on each side and log some measurements.
And maybe a temp sensor before the intercooler too so i have that data as well.

I did this a few years ago, got some pretty cool data. Back pressure, temp before and after intercooler. I have a recipe for back pressure sensor stuff if interested. Part numbers and sources and such.

I am definitely interested. I need to get my car back on the road though! I'm getting some bad ideas with all this down time! I only have 15 miles on this engine, i can't be replacing stuff already! Luckily i have a 4 day weekend next week so i hope to bang out a lot of it. My wife had knee surgery last Friday, so i had to sit home all last weekend. Way behind. I did manage to take a few minutes after work one day and got half of the rear apron cut free. Only 150 more spot welds to drill to get the other side free.

richie,uk wrote: ↑Tue Oct 27, 2020 2:02 pm

bug66 wrote: ↑Thu Oct 22, 2020 3:00 pm My 2165cc made 501whp on 32psi.

Aluminium case. 4x10mm studs per cylinder.

No fancy stuff.


32psi is not that much...

If it really made that much then why is it so slow?

Do you question the dyno, or mock the driver?

Yes. 501whp and 667wnm.

As you can see, the turbo is out of breath, and the peak rpm drops when applying more boost.

Am i misreading it, or does that say 368hp? Which to me is still impressive!

buguy wrote: ↑Wed Oct 28, 2020 3:44 am Am i misreading it, or does that say 368hp? Which to me is still impressive!

kW

Roger that.