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by **peobryant** » Sat Jan 10, 2009 5:55 pm

Everyone tells me that with an auto truck, you should go with a larger exhaust housing (i.e. 16cm) and with a manual smaller is better (i.e. 12cm). Can someone explain why? On 24 Valve automatics the turbo has a 9cm exhaust housing right? Why wouldn't an auto like smaller exhaust housings?

by **PToombs** » Sat Jan 10, 2009 6:54 pm

The thought is that autos wind quicker due to the converter being sloppy, compared to a stick. A smaller housing will spin the turbo up quicker on a stick truck, bringing the fuel on faster.

by **peobryant** » Sat Jan 10, 2009 7:41 pm

Is this only true for the 1st gen auto's then? If you had a better aftermarket converter, would the smaller housing matter?

by **Begle1** » Sat Jan 10, 2009 10:38 pm

It's true for all automatics; a lot of the serious drag racer guys run convertors that stall real high (2500+) so that they can quickly spool real big singles.

The other reason why auto's like a bigger housing, is that they only have to spool the turbo once.

Why did the second gens come with the nasty nines on automatics only? I don't know if anybody has an answer to that one... Emissions standards stricter on automatics, perhaps.

by **oconnellrb** » Sat Jan 10, 2009 10:58 pm

will it make it run to hot?I have a hx 35 on a auto truck but havent turn it up yet.
Ryan

by **peobryant** » Sat Jan 10, 2009 11:03 pm

oconnellrb wrote:will it make it run to hot?I have a hx 35 on a auto truck but havent turn it up yet.
Ryan

Depends on your setup. If you have a stock truck, or close to stock then then it will be fine. Before you start turning the pump up, you need to install a pyro.

by **oconnellrb** » Sat Jan 10, 2009 11:15 pm

i have pyro.I only seen it get up like 800.Its a 89 motor with a frist gen intercooler.I have a fuel pin and spring but not installed yet.

by **peobryant** » Sat Jan 10, 2009 11:17 pm

I would say with the fuel pin and spring, you will be fine with the HX-35. Add some injectors, and you may want to look into a new turbo...

by **Richie O** » Sat Jan 10, 2009 11:38 pm

Oconnellrb, I bet you could make 275 to 290 horses with a hx35 and your stock injectors if you turn up the pump. You sure will be 1300 plus pre turbo egt's, but it would be fun. :lol:

by **peobryant** » Sat Jan 10, 2009 11:48 pm

1300* isn't really that hot, if you're only on it for a few seconds. You don't want to keep it up there though.

by **peobryant** » Sat Jan 10, 2009 11:53 pm

oconnellrb wrote:i have pyro.I only seen it get up like 800.Its a 89 motor with a frist gen intercooler.I have a fuel pin and spring but not installed yet.

I just saw that it was an '89. An HX-35 is a pretty significant upgrade from the non I/C stock "baby" H1C's. I have heard quite a few people runnung 12cm with auto's and had nothing bad to report. That was the whole point of the thread, to understand why they supposedly don't like smaller housings.

by **SChandler** » Mon Jan 12, 2009 11:42 am

I don't think it is so much that automatics don't like it, they simply don't need it. If the converter doesn't stall until 2000 rpm, then you've got rpms to help light the converter, the housing isn't as much of an influence on turbo performance. Plus the already mentioned only needing to spool it once with an auto vs. every time you shift a manual. From a maintaining egt's standpoint, you only want as much housing as you need to get acceptable spool up. That's why guys with manuals who tow heavy run 16's and those that never tow run 12's.

by **peobryant** » Mon Jan 12, 2009 8:04 pm

No need to start another thread for this, so I'll post it in here.

I have the chance to buy a used 16cm exhaust housing for $100 plus shipping. It has about 5K miles on it. My mods are listed in my sig, and I might turn the fuel screw againt the collar.

If I get injectors I will get a bigger turbo, so it will only be used with said mods.

Think its a good deal? I need to get rid of my 21cm housing.

by **Richie O** » Mon Jan 12, 2009 8:09 pm

I had a 16 on my 89 for awhile. I liked it. I am going to put the 16 on my 93 with a GDS 60mm upgade I think. You should see a good improvement over your 21. What do the 16's go for new now? If it is in good shape and you can save some bucks go ahead. You can always sell it later to the next power hungry guy.

by **peobryant** » Mon Jan 12, 2009 9:27 pm

Richie O wrote:I had a 16 on my 89 for awhile. I liked it. I am going to put the 16 on my 93 with a GDS 60mm upgade I think. You should see a good improvement over your 21. What do the 16's go for new now? If it is in good shape and you can save some bucks go ahead. You can always sell it later to the next power hungry guy.

The site where he bought his listed them for over $200, but I have seen them new for about $170. I will probably do it, because the 21cm is almost unbearable now. Just curious, but what exactly do I have to do to swap housings?

Thanks

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