TURBO's and HOTAIR
- Thread starter Boost231
- Start date
dr_frankenstein
Mad Scientist
- Joined
- Mar 17, 2008
Well I believe that you havwe a .63 now... which should be ideal for spool, but it might be the choke point.
A .82 AR is available to swap out. Now this may increase your lag, but use of a higher stall converter should correct it.
But before we address the housing itself, i have to ask the question if your still running the factory HA elbow and wastegate assembly.... that alone could be the choke point.
A.j.
A .82 AR is available to swap out. Now this may increase your lag, but use of a higher stall converter should correct it.
But before we address the housing itself, i have to ask the question if your still running the factory HA elbow and wastegate assembly.... that alone could be the choke point.
A.j.
LOL. Nope. im running the best flowing DP a HOTAIR car has on it. Its a one off piece and it will outflow any DP for a hotair car. i will give you a little peak. in my next post
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
One of the key factors on turbo’s is back exhaust pressure.
This same backpressure also has a large affect on spool rpm, combined with the rest of the motor; Turbo, compression, cam, exhaust, heads, tune, converter, etc.
Typical street application turbo chargers have 200% backpressure.
That means; At 20PSI boost, you have 40PSI exhaust pressure before the turbo.
This makes your turbo only 50% efficient, and, decreases your effective cylinder filling.
So …………
I started working on a calculator program to determine camshaft timing, etc etc.
It will never be a “professional calculator”, but, it is amazing to see some of the cause and affect of cam timing and overlap. Which brings up the $1,000,000 question;
On a HA set-up, do you want the cam biased towards the intake or exhaust?
I started a thread on this a while back and never got any responses.
If anyone has any backpressure measurement data (boost vs exhaust pressure), I will run some more calcs and post them.
Anyway ………… since the restriction is in the turbine, a 4” DP (Example only) will not be of much benefit. Matter of fact, it could actually hurt the car as the gasses cool off with the expansion into the 4”, and velocity drops.
Anyway ………. Back to topic.
To truly determine how big of an A/R you need, you will need data.
IMHO, It is not just about HP, but a balance between HP and TQ.
Having said that, a bigger A/R on the same set-up will typically narrow the powerband, but give more HP (Peakier). The assumption here is that the car ran OK and was not choked out to start with.
My instinct tell me that a size change from 0.63 to 0.83 A/R on the turbine side, is about a +200-400 RPM stall change.
v-band yes. its getting jethot coated.
dr_frankenstein
Mad Scientist
- Joined
- Mar 17, 2008
So whats the concensus?
yes to bigger AR?
or
no to bigger AR?
A.j.
yes to bigger AR?
or
no to bigger AR?
A.j.
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
So whats the concensus?
yes to bigger AR?
or
no to bigger AR?
Are we talking about turbine housing A/R?
Well, it depends on the set-up and goal for the car. :wink:
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
Brent,
Like I said in an earlier post; If you had the data, it would allow you to make those decision for your set-up.
This is what I would do however;
Keep the same A/R, but, switch to a Precision housing.
Although the A/R is the same, it has much better flow characteristics.
The car will have a little more lag but pull HARD on the top end.
That will be my next project ........ right after all the others are complete.
Brent,
Like I said in an earlier post; If you had the data, it would allow you to make those decision for your set-up.
This is what I would do however;
Keep the same A/R, but, switch to a Precision housing.
Although the A/R is the same, it has much better flow characteristics.
The car will have a little more lag but pull HARD on the top end.
That will be my next project ........ right after all the others are complete.
dont i have a precision housing now? i got my TA-54 from precision along time ago so wouldnt it have the precision housing already? its stamped precision on the housing. i attached a picture of it.
Attachments
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
Can't see the casting, but if you already have the Precision housing, I would step it up to the next A/R housing.
Can't see the casting, but if you already have the Precision housing, I would step it up to the next A/R housing.
which would be and .85 right? also what does this do? i know it will pull harder up top and also effect spool (my car spools super fast right now). it will reduce back pressure thus changing the map correct? im new to this. im going to change the turbo in time but im just trying to dial in what i have right now with a few small changes.
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
I think that is the next size in turbine housing (not real sure).
Contact Precision to find out for sure.
As far as the map;
The different turbine housing will not change the map, since this is only an indication what the compressor wheel is capable off.
There should however be a change where the engine performs on the map, based on increased VE.
Let us know how it turns out.
dr_frankenstein
Mad Scientist
- Joined
- Mar 17, 2008
See you explained you own answer
"It Spools super fast"
that alone tells me that its moving more air than that housing can handle, need to look at it in retrospect and add up the elements.
1 Boost Creep
2 massive DP for a HA but still no real increase
3 No increase of speed considering favrable weather conditions
all of these things point towards a bottle neck at the housing.
yes you need to change the housing to a larger A/R.
A.j.
"It Spools super fast"
that alone tells me that its moving more air than that housing can handle, need to look at it in retrospect and add up the elements.
1 Boost Creep
2 massive DP for a HA but still no real increase
3 No increase of speed considering favrable weather conditions
all of these things point towards a bottle neck at the housing.
yes you need to change the housing to a larger A/R.
A.j.
Jerryl
Tall Unvaccinated Chinese Guy
- Joined
- Dec 14, 2004
A tighter more efficient converter will take care of that as well .......
But I agree, it is most likely not the converter.
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