Input on differences between 14cm/16cm EGT's

[BushWakr - RIP]

Hi Guys,



I'd like to get some input from you all on this.

My current setup is:

- 3. 5" mandrel bent exhaust

- K&N filter

- timing 15* advance

- pump adjustments all in 'moderate' range except diaphram at 'full'

- 16cm housing

- Lucas (POD's)

- DTT TC/VB/Trans.

- Governed = 2750 rpm +-

- EGT's at WOT/2700/OD/8%grade/empty approx 1050-1100*F @26 psi



Ok, the question is... how much if any increase in EGT's/boost will I see under above conditions if, I switch to 14cm N/W housing without making ANY other changes.

Second, am I likely to see high drive pressures with the 14cm N/W



Any guesses? Any practical experience with similar changes eg:16cm to 14cm ?



Let er rip... I can take it...



Thanks, Bob.

 

[McGivern]

Bob,

Can't give you your exact situation, but I just switched from a non-gated 16 to a gated 12 last week.



My driveability around town is much better. I have the gate set at 20psi right now, but I'm still messing with it. My EGT's went down about 50-100 degrees across the board, even when pulling a 6K trailer up a grade here in the AZ summer. I see about 850 max post turbine. The gated 12 is pretty easy to find. Just a thought.



Mark

 

[BushWakr - RIP]

McGivern,



850*F is not bad. Adding another 200*F for post-turbo pyro you're still only around 1050*F. Pretty decent.

What RPM's are you running and what gear are you in when you do that?



Bob.

 

[bflood]

12cm2 reduces egt?

Why does the more exhaust restrictive 12cm2 housing reduce egt's?



I would think that while producing more low end power, max egt's would increase.

 

[McGivern]

info

Those temps are in 5th gear at about 2000 RPM and just over 70MPH on a variable grade of 3-5%.



As for the logic of the 12cm being lower- I am no expert but I'm told that a nongated 16 and a gated 12 flow a comparable amount of exhuast gas. So, I figure that because the gas that is bypassing the turbine through the wastegate does not do any work when exiting, it stores less heat. I am sure that if I blocked the gate, or set it really high, that I would see higher temps than the 16. I set my gate at about 18psi, and it will peak at 20. This is all the boost I need for my towing application.



Mark

 

[Old Smoky]

So, why use a 16 if a wastegated 12 flows a comperable amount, and has much better spool-up? I know that they cost a bit more, and take a little longer to install, but the performance is much better. I thought the 12 was too restrictive, created too much heat, for applications such as towing. Now it sounds like this isn't true.



Mike

 

[BushWakr - RIP]

This is exactly why I was asking for anyone who has/is running a similar combo.

Old Smoky,

my understanding is similar to yours, but I think the one major issue that is in McGivern's favor is he is wastegating at 20 psi.

Un-gated he may well overboost, or have very high drive pressures, which cause heat problems. As I understand it, the smaller inlets on the smaller housings start to create backpressure at higher boost levels, hence the temp problems.

What I was looking for is what the practical limits were/are for a 14 NW, in terms of boost/HP levels, BEFORE those limits are reached or exceeded.

So, given my current setup, in particular, my boost level/EGT's now, how far up will the 14 take me, and will it carry me into the problems mentioned above.

I realize you can moderate boost/EGT's with fueling (rather than wastegating) but it is less effective than a WG I would think.

I'm just trying to put theoretical with practical to get a more effective expectation. Besides, it's a PITA to re-do the exhaust downpipe if the 14 causes too many EGT problems. .



Thanks guys, I appreciate all the frames of reference.



bob.

 

[McGivern]

12cm

I hope I didn't confuse the issue guys. I just wanted to sahre what works well for me. I was also told that the 12cm was only efficient upto about 250HP. But it makes sense to me that, if you used the smallest WG housing you can to get the boost you need, and then bleed off the rest unrestricted, that you get the best of both worlds. I don't think it would be your best way to go for max power.

Mark