370 large turbine 88mm back pressure results
06-25-2013, 08:13 PM
#1
370 large turbine 88mm back pressure results just share since i have been through many turbos while keeping the jist of the setup the same. tc78>78gts>pt88>hp8811
and there is alot of talk on this these days
love it, opens up cam selection alot too
motor is a 370 at 10:1 with WCCH lsa heads, run on e50 and a weird cam. 232/242-113....530/540lift
on 15psi of boost in the manifold i see 10-12 psi of drive pressure depending on rpm
only thing i would caution is it takes a serious amount of WG capacity to control it
i have two 38 MVs tial gates in perfect priority and i am right on the edge of being able to control boost, it still creeps on me above 6500rpm
put it this way..... when i had the pt88....... i could be full tilt/full boost at 6500rpm, and if i killed air pressure to the top of the gates boost would drop instantly to 0
tapped here to monitor drive pressure
and there is alot of talk on this these days
love it, opens up cam selection alot too
motor is a 370 at 10:1 with WCCH lsa heads, run on e50 and a weird cam. 232/242-113....530/540lift
on 15psi of boost in the manifold i see 10-12 psi of drive pressure depending on rpm
only thing i would caution is it takes a serious amount of WG capacity to control it
i have two 38 MVs tial gates in perfect priority and i am right on the edge of being able to control boost, it still creeps on me above 6500rpm
put it this way..... when i had the pt88....... i could be full tilt/full boost at 6500rpm, and if i killed air pressure to the top of the gates boost would drop instantly to 0
tapped here to monitor drive pressure
06-25-2013, 10:49 PM
#4
my pt4788 would spool instantly and never creep. but i am using an ams putting co2 on top of the gate. but i was seeing 1psi on the gate would give me 1 psi of boost up to 24 psi. then i would cram 1.5:1. im not sure why its creeping, its gotta be the direction its flowing.
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06-26-2013, 06:25 AM
#8
FasTimeSS, You continue to log into tech and post messages, but you still haven't shipped me the shocks I paid you for, and havent responded to any messages...........
06-26-2013, 08:01 AM
#9
Are there any converters / estimators where you can plug in things like engines size, comp., cams specs, power and operating ranges and it can give you estimate turbine sizes that would best suit the engine? Would be intresting to see what the ideal sized turbine would be. I would guess that most people are running a far too small exahust housing!
06-26-2013, 09:12 AM
#10
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Not sure what im missing here, you put a bigger turbing housing youll definitely get lower backpressure numbers, but you will kill spool and low-mid range power.
It would be nice to compare backpressure on different turbos AND comment on the difference in spool
It would be nice to compare backpressure on different turbos AND comment on the difference in spool
06-26-2013, 09:43 AM
#11
Wheel design can play a big factor on spool time by allowing greater and more effiecent surface area on the turbine wheel allowing the turbo to spool faster. Using lightweight materials on the Compressor, Turbine and shaft helps too.
Cam choice can play a big role by changing the velocity and density of exhaust gasses. Also the engine power band idealy you would want to know what volumetric flow rate range is the turbine most efficient and pick a power band for you motor based on that, really a engine is just a fancy hot air pump.
Torque converters are a factor because they dictate how fast a engine will achieve a certain volumetric flow rate and what that rate will be based off of RPM they flash at and load the engine.
Fuel type, E fuels produce a higher volumetric flow rate based on the fact roughly 30 % more is used (E-85). So you can expect about that much more flow out the exhuast.
Displacement is easy the more you have the higher the volumetric flowrate.
Gearing/ weight of car/ wind resistance all determines loading which effects spool time. ect
There is a lot to consider on turbo spool rate.
06-26-2013, 09:43 AM
#12
better to use a larger turbine wheel with a tighter AR than the other way around. Also a larger trubine wheel will require less backpresure to drive the compressor wheel than a smaller wheel for any given PSI (intake manifold presure). 
06-26-2013, 08:32 PM
#14
That large turbine wheels would be laggy. Everyone was running pt7675 turbos and it didn't seem to matter if it was a 408 or 5.3 it was the turbo to have.
If I wasn't swyping on my tablet I'd talk about overlap and how it directly affects drive pressure and how it can be manipulated into working for us and not against us.
How the valve timing is coordinated around that chosen amount of overlap is nearly just as important as not using to much or too little overlap by itself.
Maybe tomorrow...
06-26-2013, 09:16 PM
#15
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Martin, although I agree with you almost 100% of the time and value your input, I have seen a tight a/r choke a larger turbine wheel and spooled it slower. Swapped to the next size housing up and the turbo spooled better and "woke up". This was on a small frame T4.
How this affects these big turbines might be totally different. I think its a balance as pointed out.
How this affects these big turbines might be totally different. I think its a balance as pointed out.
06-26-2013, 11:24 PM
#16
the pt88 ran very well, spooled well too. the one thing i didnt like about it was it seemed to be sensitive to surge and barking
I dont think i will ever need another turbo, i enjoy this one very much
I never measured pressures on the other turbos but it was easy to see with the boost produced compared to gate spring pressure
tc78 would make 4 psi on 8psi springs
78gts was much better, close to 8 not quite on the same springs
pt88 would make 8-9 same springs
I cut 1.5 coils from the same springs and this turbo still makes 12-13 on spring pressure and holds solid till 6500 rpm where the gates reach the point of not having the needed capacity and it will creep to 16psi by 7200
it is the equivalent size of a gt55 turbine, but it is the old TV wheel, has a clip though, it isnt the straight trailing edge like most of the TV stuff
its hard to say because i changed from a cheap 10" PTC converter to a big boy 9.5 over winter at the same time. it is without a doubt harder to hit initial boost. but far from unresponsive. the converter stalls to 3000-3100 and it will build boost from that low.
it is no exaggeration when i say i have more traction with this turbo than any other previous turbo i have had on the street. something about the way power comes in
manual gauge with passenger
06-27-2013, 01:20 AM
#18
Just imagine what that thing would do with a genuine GT55 wheel...
Data mining is fun isnt it?
Are you gonna turn it up and start looking for the knee point in the ratio??
On Eds 331ci SBF we are under 1:1 up till 24 psi... 1:1 from 24 to 29..... then pick up 2:1 for the next 6 psi to finish at 35 psi boost 41 psi backpressure.
Pretty damn good for a motor thats got 29 degrees of overlap at .05, and gets spun to 8200.
Data mining is fun isnt it?
Are you gonna turn it up and start looking for the knee point in the ratio??
On Eds 331ci SBF we are under 1:1 up till 24 psi... 1:1 from 24 to 29..... then pick up 2:1 for the next 6 psi to finish at 35 psi boost 41 psi backpressure.
Pretty damn good for a motor thats got 29 degrees of overlap at .05, and gets spun to 8200.
06-27-2013, 02:56 AM
#19
I remember saying this same thing before I worked at tick and was laughed off this very board and now it's spouted as gospel. It feels good to be right sometimes.
That large turbine wheels would be laggy. Everyone was running pt7675 turbos and it didn't seem to matter if it was a 408 or 5.3 it was the turbo to have.
If I wasn't swyping on my tablet I'd talk about overlap and how it directly affects drive pressure and how it can be manipulated into working for us and not against us.
How the valve timing is coordinated around that chosen amount of overlap is nearly just as important as not using to much or too little overlap by itself.
Maybe tomorrow...
That large turbine wheels would be laggy. Everyone was running pt7675 turbos and it didn't seem to matter if it was a 408 or 5.3 it was the turbo to have.
If I wasn't swyping on my tablet I'd talk about overlap and how it directly affects drive pressure and how it can be manipulated into working for us and not against us.
How the valve timing is coordinated around that chosen amount of overlap is nearly just as important as not using to much or too little overlap by itself.
Maybe tomorrow...
Chris.
06-27-2013, 08:40 AM
#20
Just imagine what that thing would do with a genuine GT55 wheel...
Data mining is fun isnt it?
Are you gonna turn it up and start looking for the knee point in the ratio??
On Eds 331ci SBF we are under 1:1 up till 24 psi... 1:1 from 24 to 29..... then pick up 2:1 for the next 6 psi to finish at 35 psi boost 41 psi backpressure.
Pretty damn good for a motor thats got 29 degrees of overlap at .05, and gets spun to 8200.
Data mining is fun isnt it?
Are you gonna turn it up and start looking for the knee point in the ratio??
On Eds 331ci SBF we are under 1:1 up till 24 psi... 1:1 from 24 to 29..... then pick up 2:1 for the next 6 psi to finish at 35 psi boost 41 psi backpressure.
Pretty damn good for a motor thats got 29 degrees of overlap at .05, and gets spun to 8200.
Right now I am on a 2 bar OS and my injectors are done at that point
Aside from injectors the next thing on my list is a cam from the cam man since I have the turbo setup where I want it
Then turn the wick up
