6 cm^2 or 7cm^2 housing for 14b...

[belize1334]

Some of you may recall I'm attempting to compete in a "stock engine stock turbo" class so I'm switching back to a 14b. I've got an "okay" condition 6cm^2 housing as well as my 7cm^2 E3 housing that I've been using with my s16g. Now, granted, the 7cm^2 housing isn't stock on the 14b so strictly speaking it isn't legal... but I'm trying to get a collection of first hand experience on spool time and top-end between the two housings. If the concensus is that one has a significant performance advantage over the other then I'll stay legal... If it's all a wash then I'll stick with the more durable and less cracked 7cm^2 piece...

So, if you've run a 7cm^2 housing on a 14b (or if you just have a working knowledge of the setup) then please chime in with thoughts on spool-time, top-end, ultimate power potential, etc.

 

[TurboTrader]

I 7cm^2 housing can help a 14b quite a bit, especially by porting the manifold out to 7cm as well. You will sacrifice a few hundred RPM on spool, but will pick up a lot up top where the 14b usually falls flat on it's face. Provided you have the fuel for it, you should pull hard all the way through redline and then some.

 

Is this autocross racing you're doing? I ran an FP Evo 3 7cm housing on a 14b for awhile. Spool time increased and I didn't notice a big top end difference. I did just swap out that 7cm housing to a 6cm housing on my s16g and noticed a huge difference in spool with no noticeable difference in top end. Right now I'm back to a 14b with a 6cm housing.

If you're doing some kind of road racing or autocrossing and can't upgrade cams I would stay with the 6cm housing and maybe port it a bit. This way you'll keep the better spool characteristics for a little more mid range. I think with stock cams you would never notice a big difference in top end between a 6cm and 7cm housing. In my experience it seems power dies at about 6500 no matter how much boost or how many mods when I use stock cams.

Drag racing I would go 7cm.

 

[NateCrisman]

I picked up about 3mph going to a ported E3 7cm housing from an unported 6cm housing at the dragstrip. The car was 134lb light on the second time at the track, and was running pretty much the exact same boost/tune. So I would figure about 1.5mph from the 7cm housing

 

Quoting MadBeachDSM:
I 7cm^2 housing can help a 14b quite a bit, especially by porting the manifold out to 7cm as well. You will sacrifice a few hundred RPM on spool, but will pick up a lot up top where the 14b usually falls flat on it's face. Provided you have the fuel for it, you should pull hard all the way through redline and then some.



really? mine spooled faster when i had the 7cm exhaust housing on my 14b, it was quite fun actually /ubbthreads/images/graemlins/grin.gif

 

The only back to back I have is from my s16g, but going from a ported 7cm 2g manifold and FP 7cm housing to an unported 6cm housing and unported 6cm manifold I dropped spool by an easy 300-400 RPM. Putting the 14b back in dropped spool by another 100-200 RPM or so.

 

[belize1334]

Yeah, it's autocross. And you're right, with the stock motor the stock cams are also required so there's not alot of cam to play with... though I can tweak cam timing a little if that helps.

Nate: What kind of power characteristics would you associate with your estimated 1.5 mph trap? Clearly you increased the area under the curve but is it shifted more toward the top? Did it let you hold more boost to redline or did it just push more air at the same boost? You probably haven't payed much attention to boost-threshold for the too setups but do you feel like the boost comes on slower with the 7cm?

 

[Ian M]

Back when I had a 14b on my car,I heavily ported my 6cm housing out to the 7cm gasket size,along with the 2g manifold. It's been years,but I recall comparing it with a freinds ported 7cm,and it ended up very similar. I also belled the outlet to "2.5.

I don't know what part if any the housing played in how well the car ran,but It spooled very fast and hit hard for what it was in that configuration. It was fun to drive,and the 1st and 2nd gear roll on snappiness made it feel faster by seat of the pants than it actually was. The car went 12's pretty easily,and the car was still pretty close to stock at the time.

 

[NateCrisman]

Quoting belize1334:

Nate: What kind of power characteristics would you associate with your estimated 1.5 mph trap? Clearly you increased the area under the curve but is it shifted more toward the top? Did it let you hold more boost to redline or did it just push more air at the same boost? You probably haven't payed much attention to boost-threshold for the too setups but do you feel like the boost comes on slower with the 7cm?



I don't think it added any significant "top end" at all, if anything it made a good 10hp more across the board once on boost. The 7cm housing is not some magic trick that turns a 14b into a high rpm beast, it's still worthless past 6300rpm with stock cams. As far as spoolup, I couldn't tell any difference at all. The turbine housing doesn't seem to have a "dyno plot shifting" effect like cams or a smim where it adds useable rpm.

This isn't anything I would say is a major change or important choice. 5-10hp isn't going to make or break you, nor is 100rpm of spoolup. If you think the 7cm housing being "not stock" is going to get you into any trouble, then I'd just put the 6cm housing on with a decent port job and be comforted that your not giving up any huge amount of power or useable rpm. If you can get away with the 7cm housing, it's worth using but I wouldn't stress out over it.

In an Autox car, I just can't see 10hp being anything that is going to have a real serious effect compared to the driving/tires/suspension/weight factors. If anything, the miniscule spoolup might be worth more than 10hp anyway if it helps get the car out of tight turns just a little earlier vs the accel that 10+hp makes the few times your really wot for a stretch.

 

[belize1334]

^^ That's basically my thinking. I've been surprised by the hundreds of rpm spool difference that people quote but I think alot of that is switching from a rotted-out housing to one that has better wg sealing. At this point, my ideal situation would be to determine that there is no appreciable performance advantage one way or another in which case I'll use the 7cm just cause it's newer and not cracked. I just wanted to make sure that there's no 30hp or 500rpm spool difference which is gonna be either a performance detriment or an arguable advantage (which could be protested and get me into trouble). I think at this point I'll just call it a wash and go with the one that's in better condition.

 

[H05TYL]

^I agree, it's amazing the difference a tiny leak at the w/g can make - I dropped spool time by 800rpm on the exact same turbo by fixing a bent actuator rod that was holding the wastegate open

 

[NateCrisman]

Quoting belize1334:
I think at this point I'll just call it a wash and go with the one that's in better condition.



Yup, I don't know how I missed saying that, but I would run which ever turbine housing has the best clean threads on the bolt holes and the least cracks around the wastegate seat. for drag racing, you can deal with it, but for autox, your going to want the best seat on the wastegate to help the spool on tight corners that you stay in 2nd but drop down to low rpm.

I have a really really nice condition 6cm housing that isn't cracked in the event you think the 7cm is going to cause you "legal problems" for your class.

 

[belize1334]

^^ How much would you want for that 6cm housing?