Payson, AZ Turbo pull off *Round 1*

[WarWagon]

Payson, AZ is at 4900'. From Phoenix, AZ it is literately uphill both ways. Before you get there you have a 6.5 killer hill. I have blown 1 engine in this area and purchased another 6.5 that blew the engine in this area towing.

Today we borrowed a 1800 LB dump trailer and took a run at this mountain pull.

Round trip was 156 miles with 15 gal used on the nose filled before and after to the curve in the filler neck. 10.4 MPG. Average moving speed was 59 MPH. Towed a 1800LBS 2 axle dump trailer for an extra load. (My 1993 with the GM3 did not do better than 8 MPG and was logged at 7 and 7.5 MPG...) In town economy before I started this venture was 15 MPG - not towing. The pickup with the GM3 would be 13 in town and 14.x freeway.

Bottom line: I slowed down for the corners and nothing else! The mountain pulls did not slow me down. I was at Full Throttle asking for more power only twice, but, over 55 MPH both times. The fan only came on twice the entire trip a vast improvement vs. roaring on every hill the GM3 would do in similar outdoor temps. With the ATT the Suburban does not perform like stock. The biggest improvement is having power all the way to redline instead of the loosing power with higher RPM the GM3 would give me.

Max ECT was 215 and the Kennedy fan kicked out at 180 ECT. (A lower than 195 single T-Stat appears to be required to make the fan work properly. I use a 180.) IAT peak was 270 degrees F.

This engine is a 1986 6.2 complete with 6.2 military heads and precups. The precups had us hit a boost "wall" at 17 PSI no matter what we did with fuel and timing. It simply would not burn more fuel and generate boost with it - it just turned more fuel to smoke. Simply put the NA cups are not big enough. The slightly higher compression, 6.2 injector angle, and larger exhaust valves can also factor in. So a 6.5 set of heads with 6.5 turbo precups will do better. In fact my second 1993 had a rebuilt engine with 6.5 NA precups in it. So sometimes you don't know if someone swapped out a 6.5 turbo with 6.5 NA heads. This is another factor to be reminded of and further proof that the biggest turbo precups you can get are the best for maximum air.

 

[JiFaire]

Interesting thought about the precups, WW... you're thinking the newer (turbo) engines wouldn't have this issue, if I understand you correctly?

I like the extra mileage you're seeing! In today's economy, the price of fuel is going to add up fairly quick to help pay that bad boy off. 2+MPG difference towing is a big difference (~ 100 gallons, or $380) on a 4000 mile holiday ... that's half the turbo investment right there!

The power while staying cool is another huge advantage, obviously; how did the truck react at higher elevations? Did you notice problems getting enough air (like more smoke, or lag?)

 

[WarWagon]

Turbo engines should not see much of an issue with any turbo precup. The last diamond design that is the current choice would be the best when going for large turbo's. However 6.5 NA precups work, but, are not the best. The 6.2 NA precups hurt you - even the largest military J code emissions exempt 6.2 NA cups. Simply can't move enough air through the NA cups with the time allowed regardless of timing or fuel.

Possible a 6.5 TD engine was replaced by a 6.5 NA engine junkyard pull. I ran into this with my 2nd 1993. I am in fact testing out the 1995 6.5 NA precups on my 1993 pickup now with an ATT.

Altitude affected my EGT's although I was limited by the precups and couldn't do much with it. I have a near smokeless tune over 2K at altitude.

The withholding of information on another site about the ATT has cost me a lot of money in fuel. Money I could have been spending with their vendors went to fuel instead!!! GM's choked turbo design may have been the source of the problem, but, other sites were not helpful in solving this 'known' problem. ~$200 A DAY in fuel! 3MPG over 550 miles a day is a red/green bottom line difference. Bottom line is these sites are supposed to be helpful to the members and in this role, vendors or not, they choked badly and intentionally when it mattered most - to me and my business. There is another well respected Diesel supplier that is stuck on GM8's with TM's. I did not get anywhere near as good of results using their products.

 

[NVW]

The ATT does work well, I don't pull that often but when I do it's with a GVW of 25-30k lbs. I would never go back to a GMx.

 

[btfarm]

This is the run up 87? I've done that in an anemic rental car. At least then I have a good feel for the trip.

 

[3500GMC]

Round ONE ding ding..

Good read, sounds like you've found a good combo. :thumbsup:

 

[WarWagon]

Yes up 87. You know how hilly that is before even getting to the 'big pull' and explains the reason the MPG is so bad... There are 6% grades up and down all the way to it.

 

[Rhinopkc]

What was the ambient temp? What EGT were you seeing?

 

[WarWagon]

Ambient temps were 70 at the start and lower in Payson. My advice is clear to any 6.2 owner putting an A Team on - replace the precups with larger 6.5 turbo ones. When we hit 'the precup wall' EGT's were not pretty. Of course we were using a hot tune and attempting to get all we could out of the engine. As this is from the precups and not the fault of the turbo I am not posting them. I think I am the only ATT user with 6.2 heads.

However, For the 1993 My EGT's with a GM3 were high on this run when I was delivering parts: 1400 for extended times. When I recently put the ATT on the 1993 it went from 1250, GM3, to 1100, ATT, in town with WOT blasts. (We are at ~2000') This is the normal result with 6.5 precups and an ATT.

 

[micky_blue]

That is a good pull. I will be doing it right after Christmas in my Yukon towing a couple thousand pounds of furniture to Philly. Another good pull if above Black Canyon City up to the rest area.