T3/T4 A/R Ratio

[Gyrhead]

Just trying to spec a new turbo for my Bolo car and still trying to get my mind around the .48 vs .63 A/R for our cars. I kind of like the quick spool up of the stock turbo and am worried that a .63 might be too much and result in a ton of lag. The motor is basically stock internals with a Ranger roller cam, Ported E6, 255 pump, Kirban AFPR a Forced 4 FIMC, CAI and BPV and a Sac Mustang 3" DP. Still running stock 35 # injectors and stock TB. What have folks in our world been reporting with their T3/T4OE combinations? How much does compressor A/R affect performance vs turbine A/R? Just trying to get educated.

[Raven855]

Here is a good read for you. http://forum.turboford.org/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=4;t=000050

[SVO86]

I have a nos 60 ar63 Im about to install will i see alot of lag over the stock
ar48.

[Raven855]

It is hard to answer without knowing your setup, but I would say your boost will come on 400 to 500 later on average.

[86svo9l]

I run a T04E .63 with 3" downpipe, tube header, BoPort 1.9 and a few other things. Full spool by 3700, which is much more laggy than stock, but it pulls like a train when it does spool.

[Raven855]

How do you like that 1.9 cam?

[86svo9l]

Love it.

[Raven855]

How does it compare to others cams?

[86svo9l]

I can only compare it to stock. As far as driveability goes it drives just as well as stock(after the tbody upgrade), it sounds great, and it pulls hard from 3k on and does not run out of steam like the stock cam does.

[Raven855]

Thanks for the info and sorry about the hijack. I have a t3/t4 50E trim with a 48 stage III. Love it. It has recently been rebuilt by Evergreen and should flow closer to 50#. Waiting to be installed......

[IXLR8SVO]

Along with knowing your set up..... how will you be driving your car?

Do you need the boost early in for more stop & go -or- will you need your boost up higher up the RPM at freeway speeds for passing.

My Evergreen T03/T04 Turbo in my SVO rides on a 48AR. Most of my SVO driving is below 50MPH on twisty canyon roads.
With an identical setup in my TurboCoupe freeway cruiser, I use a 63AR

[SVO86]

I have almost the same exact setup as gyrhead but only thing I have different is
I have a larger throttle body kit I do a mixed highway and stop and go around town
are there any other options to get the boost to come on earlier? with the 60 ar63
or Ill just have to live with the lag.

[Stinger]

I've seen no mention of the actual turbine wheel size and it's correlation to the size of the compressor wheel size. This has just as much or more effect on the spooling characteristics as the a/r of the housing. There are 4-5 "common" turbine wheels used on a typical <400hp 2.3T engine and they can't be compared directly to each other, even with the same a/r housing. To add to that, Evergreen is known to "clip" the turbine wheel on many/most of their turbos which results in more peak flow out of the turbine at the expense of more lag time (due to the decreased efficiency created by removing part of the turbine wheel). Clipping is actually something that most turbo shops fazed out by the mid 90's as more efficient (higher flowing) turbine wheels became available. They would flow the same as a "clipped" old wheel while offering quicker spooling characteristics. So for example, comparing a clipped Stage 3 T3 turbine wheel with a non-clipped Stage 3 T3 turbine wheel when both are in a .63 a/r housing is apples to oranges.

Additionally, the compressor wheel and the exhaust/turbine wheel need to be matched in size. Too large of a compressor relative to the turbine side and you'll get slow spool, as well as a turbo that can't flow enough air out the exhaust side to support the flow of the compressor. Too small of a compressor relative to the turbine side and you'll get slow spool, as well as a turbo that can't flow enough air through the compressor side to efficiently spin the large exhaust wheel. On these setups, it doesn't matter what a/r the exhaust housing is, they will not perform as well as a properly matched setup.

The addition of GT series, billet machining, and extended tip technology in turbocharges in the last 10 years only added more options for compressor and turbine wheels that don't have to rely on 60's/70's turbo technology (T04B compressors and clipped turbine wheels) and results in greatly increased turbo efficiency for improved performance at both low rpm and high rpm as well as low and high boost pressures.

[MikeFleming]

... get my mind around the .48 vs .63 A/R for our cars.
...
The motor is basically stock internals with a Ranger roller cam, Ported E6, 255 pump, Kirban AFPR a Forced 4 FIMC, CAI and BPV and a Sac Mustang 3" DP. Still running stock 35 # injectors and stock TB.
...
How much does compressor A/R affect performance vs turbine A/R? Just trying to get educated. So you've basically got a lower-than-stock airflow capacity in a stock motor. Easy answer - use the 0.48 turbine side.

Relating the effects of turbine versus compressor sides is a VERY complex subject. Stick with a stock or slightly larger than stock (maybe up to 35 Lb/min) compressor wheel - nothing more as the engine won't eat that air. Going larger will result in increased lag all by itself and the boost will be very difficult to control - like using the 3000 PSI helium bottle to fill balloons (rather than one with a flow/pressure regulator).

Note that the 0.63 and 0.48 housing have the same exit hole size - 2.0" and use the same turbine wheel (on all the stock SVO blowers). the only diffeence is the size of the scroll area - how the exhaust gases transfer from straight line to go around and through the turbine blades.

Since you've done nothing to INCREASE the engine's airflow, don't install a bigger turbo. Your largest restriction just now on airflow is the RR camshaft. Change that before doing anything else.

[SVO86]

Mike so your saying just reuse the 0.48 housing? Ive tried to remove an exhaust housing one on a spare turbo and some of the bolts just snap off inside the housing. I have a nos with the 0.63 exhaust which will dismantle very easy my problem will be getting the 0.48 off the original . Ill try it.
Thanks
Rob

[MikeFleming]

Yep, old bolts that have not been properly maintained often break off after they've been high-heat cycled thousands of times. Use a drill press and appropriate clamps or a mill to drill out the broken studs and a cleaning/bottoming tap to clean the threads up (8mm x 1.25mm standard thread). Then replace them with the proper high-temp steel fasteners and use copious amounts of high-temp anti-seize lube during assembly.

Proper maintenance requires replacing and lubing those bolts periodically.

[65ShelbyClone]

I have almost the same exact setup as gyrhead but only thing I have different is
I have a larger throttle body kit I do a mixed highway and stop and go around town
are there any other options to get the boost to come on earlier? with the 60 ar63
or Ill just have to live with the lag.

This is all much ado about nothing.The .63 housing isn't going to make your T3 a slug. My car came with a .60/.63 and it's not hard to get it into boost nor keep it there. It comes on fast enough for the BCS to get involved.

I don't think either your setup or Gyrhead's warrants a hybrid either, especially not with 35lb injectors. With a TO4E compressor and larger T3 turbine wheel, I would be inclined to use a .63 housing anyway to help a little with turbine drive pressure.

[Stinger]

I agree. I've only seen a difference in spool time of 150-200 rpm between the two housings and the .63 makes more power after 4k. I also always tell people that with stock injectors, the "best" turbo is the .60/.63 T3 since it maxes out at a bit higher hp than the stock injectors. No reason to add a larger turbo, more lag, and handicap it with stock injectors. Just results in a less fun car overall.

[SVO86]

Just finished nos turbo install with the 60 63A/R over the old 60 48.A/R I have to say I like it much better all around!