small exhaust wheel causing backpressure?

[street6]

In the process of tuning my new build (in sig). The motor has a rather odd roller cam (205/220) with lots of exhaust duration. I'm using a fairly new T-netics TE60 (.63 a/r) and I'm looking to run about 23-25 psi with alky and pump gas. Even though I have no EGT gauge it seems my exhaust temps have risen since my old set up which was stock block/head with same turbo/boost/alky & fuel.

I'm starting to think that the small turbine wheel on the TE60 is sorta restricting exhaust flow. I have enough converter stall for a larger turbo but don't want spool issues either.

If I were gonna swap turbo's to aid in better exhaust flow would I be better off going with a larger turbine wheel or the larger exhaust housing? I think doing both would kill my spool up. Due to funds I was thinking journal bearing.


Precision billlet 62-62 with a .63 a/r
62-62 with a .85 a/r
62-65 with a .63 a/r

Suggestions , comments?

 

[RUQWKNF]

Couple of questions.

- Is this a stock bore 231 motor? Or has it been bored 30 over to 235 CI?
- What torque converter do you have?

That is definitely an odd ground cam and I can see where it might cause your EGTs to increase, especially with 23-25psi.

If you have enough converter to spool something larger, then by all means, I would consider a turbo upgrade. Especially with that cam and ported heads.
The 6262 would be a nice choice, but honestly, if you have enough converter, I would say a 6265 would work even better.
Larger turbine wheel, less back pressure and more power potential.
For either model, I would go with a .63 A/R turbine housing if it's a real street car. Now if you had a converter with alot of stall and you were wanting to make the most power possible, I would spec a .85 A/R turbine housing.
But honestly, without having back pressure readings to compare by, we are only guestimating.

The general rule of thumb is, once you have exceeded the 2:1 ratio of back pressure vs boost pressure, something has to change.
2:1 means, if you are running 25psi of boost and your back pressure is 50psi, you are done and it's time to upgrade or change the combination.

Patrick

 

[street6]

Thanks Patrick,

The block is bored 20 over, and I'm using a Pat's 9.5" NL 3000 converter.

With the TE60 and the Pat's converter I'm right around 2600 rpms @ 0 boost however the converter will stall alot more than 2600 rpms. I can build about 9psi at the line without going crazy. With a 6262 (.63 a/r) I was thinking I would be right around 2900 rpms @ 0 boost and still be able to spool 5psi at the line without trouble.

What trim are the 62 and 65 turbine wheels?

stage 5 and p-trim?

How much more stall is required for the 65 as opposed to the 62?

 

[bison]

Post some quarter mph numbers. The 60 should be able to go mid 120's before you have severe back pressure. The 62 and 65 trim wheels are a completely different design that work great at adding power when the back pressure truly was an issue. You will need more converter to spool them. The wheel type has more effect on the backpressure if your near excess.

 

[street6]

thanks.

hopefully I will get to the track either wed or fri (next week) and will post some 1/4 logs.

scratched cornea kept me out this week.

 

[street6]

Went to the track last week and only got 2 runs in.

First run (22 psi w/ 21* timing 1st/2nd and 19* timing 3rd) 12.1 @ 110 mph, soft 4psi launch, however I did get out of it around 1000 ft. (false knock). 1/8mile speed was 90 mph. (alky & pump gas with PLX w/b afr tracking set to 10.8)

Car was shifting early around 5000-5050 rpms. I have since pulled the governor and I'm having it modified for 5600 rpm shifts.

My IAT reading (sensor positioned in up pipe before the alky nozzle) at staging was around 78 degrees (outside temp approx. 72 degrees) and at the end of the run it was at 101 degrees. does this sound excessive like the small turbine wheel can not keep up with the exhaust exiting and is restricting flow???

When I'm cruising at highway speeds (2500-2800 rpms/ no boost) I usually get IAT readings only about 5-8 degrees above outside temp. However as soon as I get into boost IAT readings climb quickly.


I'm sure the IAT's will climb even further once I get to 5600 rpm shifts. Can anything be said with the IAT's I provided?

Thanks,
Kevin

 

[RUQWKNF]

Well, here's a couple of things that jump out at me with your combo and tune.

Your mph being 110 is definitely due to lifting. 21* 1st & 2nd and 19* in 3rd are very conservative timing levels even for pump gas and alky. The TE-60 is capable of making good power, but you need to run the boost higher than 22 psi and launch the car harder. Here's what I mean.

My old Blue T's quick run down, Stock 94k mile motor with valve springs, dr timing chain and an RJC power plate, RJC bleeder valve, TE-60R (same turbo you have, but with a dual ball bearing chra) adjustable fp regulator, Kirban plug wires, Autolite 23 plugs, hot wired Walbro 255lph intank pump, 60# Mototron injectors, Turbo Tweak chip, PTE stock location IC, 3" MAF pipe, stock MAF with K&N cone filter, 3" THDP, dual 2.5" cat back with Welded Ultraflow mufflers, Pat's 10" 3000 converter, stock rear upper and lower control arms, dual air bags, stock posi rear end, large rear sway bar, Mickey Thompson ET Street 27x10.5-15 tires on stock T wheels. 3670# with driver.

http://i78.photobucket.com/albums/j96/Patricks_cars/87 Turbo T Sarah/Sarahattech.jpg

http://s78.photobucket.com/albums/j96/Patricks_cars/87 Turbo T Sarah/?start=all

My tune was simple, fuel pressure set vacuum hose off at 45psi, pure C-16 race gas, 26* timing in all 3 gears and 26psi of boost. Plugs gapped at a tight .032. On my best run, O2s were .750's with zero KR. 78* ambient temp. Best pass: 11.72 @ 115 with a 1.65 sixty foot, launching with 12psi.
This was back in 2007 at the GS Nats. Very simple combo, on a stock motor.

So, by looking at your setup, you have mph to be gained with higher boost levels, upping the timing and either finding the sweet spot for alky/pump vs timing, or going with straight race gas and high timing. And you definitely need to address the shift points too. 30psi is about the limit for a TE-60 turbo, even though some have run it higher than 30. It has pushed full weight Buicks into the 119-121 range at those boost levels on combos similar to yours.

Your lifted run could have possibly been in the mid to high teens as far as mph is concerned. Next time out, for the first run I would either launch harder and break into the 11's running it all out the way it is. Then, slowly start raising boost / timing or both one increment at a time, paying close attention to your KR.
Hope some of this helps and sorry for being so long winded.

Patrick

 

[street6]

Well I definately plan to run more boost once I get this tune squared away. The reason why I'm running such low boost and timing is because I'm seeing a good amount of knock with higher boost & timing on the new build (not on the shift either). This is why I was inquiring about excessive or higher exhaust temps which I thought may have been caused by the small turbine wheel restricting flow. It seems as though my exhaust temps have raised since this new motor and set up was installed (in sig). So the rise in exhaust temperatures I'm seeing is not excessive??

I'm using a PLX w/b with target afr which is set to 10.8 (thought this would be a good starting point). My target usually stays within .2 during a run so what else could be causing the knock?

Could I have an injector leaning out at higher boost/timing levels giving me knock but still show good w/b readings? The 60's I'm using were purchased used w/ approx 1000 miles on em'.

Where do I go from here? I'm sure after I get the modified governor in the car will run in the mid-high 11's (since it went 12.1 getting out of it) but I still wanna see what the car will do with more boost and timing.

Maybe pull the plugs and see what they tell me?? I really just thought it was the raised exhaust temps keeping me from running more boost & timing without knock. But maybe not...

I like it when your long winded.......I learn more:biggrin:

 

[TurboDave]

Since this is a new build, is it possible that enough milling/machining done to the heads and block to raise the compression ratio to an abnormally high level?
What's the chamber volume on the heads? dish volume on the pistons, etc.?

 

[street6]

not sure because I purchased the block already assembled. however I was informed by the engine builder himself that the block contains custom je pistons which were fitted to retain the stock compression ratio. the build sheet provides dish style je pistons, 3.820 bore, with stock compression height and ratio.

 

[Boost231]

whats the best way to log exhaust back pressure?

 

[street6]

Well if it is indeed exhaust back pressure it must be specific to the roller cam I'm running (205/220) because several TE60 and TE44's are running much faster with stock cams, higher boost, more aggressive timing, and no KR. When this same TE60 was on my last set up (stock motor/ heads, and same exhaust system) I could run 25 psi with 23/21 timing on 93 & alky with no detonation.

If anything I figued the new set up (205/220 roller cam and race ported heads) would have less backpressure since they have the ability to flow better.

The roller cam does have high lift with 1.65 rollers so could this be a possibility why I am not able to run as much boost without detonation (compared to my old set up using the same fuel-93 & alky)???

 

[dr_frankenstein]

Are you using a dump tube or is the exhaust still hooked up?

maybe you have a plugged cat if your still hooked up.

or if you have luck like me, you hit a speed bump and crushed the bottom of your DP.

A.j.

 

[street6]

Are you using a dump tube or is the exhaust still hooked up?
maybe you have a plugged cat if your still hooked up.
or if you have luck like me, you hit a speed bump and crushed the bottom of your DP.



3" THDP (uncrushed..haha), no cat, and 2.5" exhaust.....no problems there.

 

[Mr.Spool]

street6,i doubt highly the t60 is your problem.your mph suggests the car is not making power as 22psi on a stock motor should go faster than 110,check your alky pump i would guess the motor wants more octane.if you are knocking at 100mph that is not good.what i would try is to throw some race gas in see if the knock goes away,i don't know much about the capabilities of the smc kit single,so try the race gas 1st then if the knock goes away you know you need more alky,i wouldn't throw any more boost at it untill the knock gage reads 0.try the octane 1st