Turbo delay.

[CBFryman]

try running 30lbs of boost on anything but a T3 or T4...very hard...

[tran_nsx]

hhhmmm, heres an idea. mate the compressor u got now to a smaller turbine, should reduce some lag. don't know why people haven't thought of that yet??? and/or spend some more money for some ball bearings.

[958Rocky]

cbrfryman: I assume you were referign to a t3/t4 since T3's aren't all that big. However that was my point its hard to boost 30 lbs on a regular size turbo, I thought you were claiming that you could always increase the boost by increasing the turbine speed, and obviously you can't do that indifnately since it would destroy the turbo. saabjohan was refering to turbo compounding for disel trucks which alows massive amounts of boost.


Tran_nsx: It sounds like your talking about a T3/ T4 setup to me. The turbine is from a T3 turbo ( used in passenger cars) and the T4 part is a large compressor.

[tran_nsx]

Originally Posted by 958Rocky

Tran_nsx: It sounds like your talking about a T3/ T4 setup to me. The turbine is from a T3 turbo ( used in passenger cars) and the T4 part is a large compressor.

theres different variations, but the most popular t3/t4 hybrid is an example of what im talking about. im not trying to influence him into getting this exact turbo since this is for a mercedes and not for a sport compact. he says all he wants is to reduce lag, nothing about making power, so a smaller turbine is what he really needs mated to his factory compressor.

[958Rocky]

Oh sorry man I never read the orginal topic, so I assumed you were curious why no one ever thought of that idea at all. Lol my bad

[SaabJohan]

All diesel engines are not state of the art with electronic control variable geometry turbines. Also, if you're building a high performance diesel there is usually no need for variable geometry, and in racing it's sometimes forbidden. Take a look at the Ricardo-Judd V10 turbodiesel for example, 600 hp at 6000 rpm, two fixed geometry turbochargers feed the engine with pressurized air, the turbochargers are equipped with inlet restrictors according to regulations and they doesn't use wastegates.

Variable geometry turbochargers are usually also sensitive to high exhaust temperatures.

Garrett Variable Nozzle Turbine


The reason that you don't mix a large compressor with a small turbine is that they simply don't match. The small turbine use high speeds, work with low massflow rates and makes a low power. The large compressor work at lower speeds, work with high massflow rates and consumes more power.

Garrett T3 and T04 are really old stuff, altough they have been further developed they are originally back from the 60-70:ties. There are much better turbochargers availible today.
Using high boost pressures isn't that strange, it's just a different compressor design that must be used, one that work only under more narrower conditions. The turbine output must also be optimized. This is usually done by using a larger turbine, often matched with a smaller turbine housing.
Most smaller turbochargers are matched for small gasoline engines and aren't built fo higher boost pressures, that isn't the case with for example the larger of the GT turbochargers from Garrett or the HX series from Holset. Typically special "high pressure ratio" compressors are also availible, for example Holset offer HPRC in cast titanium.
Many small turbochargers also doesn't have bearings with are designed for higher loads caused by high pressure ratios, many small Garrett turbochargers do for for example use 270 degree thrust bearings while other turbochargers are equipped with 360 degree thrust bearings or even ceramic ball bearings.



A compressor map showing the principle, it's on german since I took it from BorgWarner Turbosystems homepage (the brands KKK and Schwitzer).

X-axle - volume, or massflow

Y-axle - pressure ratio

Pumpgrenze - usually refered as surge-limit limit in english. This line cannot be crossed as it leads compressor surge, that it the air stalls in the compressor and the compressor can no longer pump air.

Stopfgrenze - usually called choke. Passing this line will not increase the flow from the compressor due to that sonic speeds have been reached in the compressor. From this point on all extra volume flow measured after the compressor, or boost comes from that the air is heated, mass flow or volume flow before the compressor will not increase. Power output from the engine will also not increase.

blue-green-lines - this is the adiabatic efficiency of the compressor. This relates to how much the air will be heated and the specific work required by the compressor.

red-lines - this is turbocharger speed, the highest of the lines is the maximum speed. Note that the highest speed isn't equal to the highest pressure ratio (boost). Maximum flow is reached at 200k rpm and a pressure ratio of about 2.1 while 180k rpm is enough for the same pressure ratio with 80% of maximum flow.

The problem with using nitrous with turbocharging is usually because the turbine won't handle the higher flow. Running with the wastegate open is not only inefficient, many original wastegates can't handle much more than the original flow. I know other people which also knows quite a lot about turbocharging and they have had similar concerns. In some cases even what the "tuning companies" use can be enough to cause concern, and in some cases the airflow isn't enough to match their power claims.
When the car manufacturers do their development they usually fit them with sensors for exhaust temperature as well as turbocharger speed.

[tran_nsx]

Originally Posted by SaabJohan

The reason that you don't mix a large compressor with a small turbine is that they simply don't match. The small turbine use high speeds, work with low massflow rates and makes a low power. The large compressor work at lower speeds, work with high massflow rates and consumes more power.

who says u can't mixed smaller turbines with bigger compressor? where have u been?

[forcefanajd]

Originally Posted by tran_nsx

who says u can't mixed smaller turbines with bigger compressor? where have u been?

wut do u think a t3/t4 turbo is??? its a t3 flange and turbine side with a t4 compressor side.

[tran_nsx]

Originally Posted by forcefanajd

wut do u think a t3/t4 turbo is??? its a t3 flange and turbine side with a t4 compressor side.

i already know that . read the guys quote and my reply again.

oh and here is the proof for saabjohan :
http://www.turboneticsinc.com/t3-4.html

[Metalli<a]

WOW WOW people back to the topic, nvm do whatever. i got it figured out, 3 inch muffler system (entire system manafold and all) td04 turbo (spools at 1500 prm i belive) wider intake, blow off vlave canvert to manual trans. well thats it thanks all.

[SaabJohan]

The T04B and E compressors used are only slightly larger than the original compressor. Also, these turbos usually don't work so well in high boost applications when powerconsumption from the compressor increase. Take a look on the turbochargers used in F1 during the eighties, large turbines fitted in small turbinehouses to improve turbine efficiency and then a quite large compressor to that. Or why don't look on how a turbocharger looks on a diesel for a truck, large turbines which can power the compressor efficiently.

The basics behind matching is the same as for jet engines.
http://www.grc.nasa.gov/WWW/K-12/airplane/ctmatch.html

[454Casull]

Originally Posted by forcefanajd

ok first things first....superchargers and turbos are completely different...turbos are basically "free horsepower" meaning it doesnt take any power to drive one.....it is driven by the exhaust to force air into the motor.superchargers are belt driven and it takes horsepower to drive one....this is a poor example but on drag cars it take i believe 600 hp to drive the supercharger on those cars(correct me if im wrong). all i can say about this is to read up a little about each of them and youll understand wut ive said a little better.

as far as freeing up some lag that youve got....you should have plenty of room to run a 3 inch exhaust system....for turbo cars you want to open the exhaust as much as you can....you lose a little bottom end but you turbo spools much faster thus making your power sooner and longer through the power band.

First thing - turbochargers ARE superchargers. The difference is that turbochargers are driven by a turbine which is powered by the exhaust gases, whereas superchargers (the contemporary usage of the term) are driven by a belt or chain off the crankshaft.

Second - turbochargers do not compress the intake air for free. True, they ARE powered by the exhaust flow, but some power (efficiency?) is lost since the exhaust doesn't flow as well.

Not many crank-driven superchargers take 600HP to run - the exception being the Roots blowers on Top Fuel dragsters. They can eat up to 800HP.

I'm not sure about the exhaust advice - I'll read up a bit on backpressure and such and I'll try to edit my post if necessary.

[tran_nsx]

Originally Posted by SaabJohan

The T04B and E compressors used are only slightly larger than the original compressor. Also, these turbos usually don't work so well in high boost applications when powerconsumption from the compressor increase. Take a look on the turbochargers used in F1 during the eighties, large turbines fitted in small turbinehouses to improve turbine efficiency and then a quite large compressor to that. Or why don't look on how a turbocharger looks on a diesel for a truck, large turbines which can power the compressor efficiently.

The basics behind matching is the same as for jet engines.
http://www.grc.nasa.gov/WWW/K-12/airplane/ctmatch.html

for a sport compact, a t3/t4 hybrid turbo is the best for street purposes hands down and yes they match.

[SaabJohan]

Originally Posted by tran_nsx

for a sport compact, a t3/t4 hybrid turbo is the best for street purposes hands down and yes they match.

T3/T04 are old designs, there are better ones today, I wouldn't spend money on these old turbos.