Compound Turbo WOT EGT

[kzimmer]

Those of you with compound turbos, what are you seeing for exhaust temperature at full throttle? At what point do you stop adding fuel and just accept the fact that you are out of air? Not concerned about drive pressure or turbo sizes at the moment, just exhaust temperature.

 

For example, With DAP 7x.013 VCO nozzles set to pop around 315 Bar, with Max canbus fuel command and 1200us of wiretap, I'm seeing a peak of about 1355°F EGT at just over 60 psi. Without the wiretap, It's less than 1200° at 50 psi or so. Is it worth adding a little more wiretap?

[Bullet]

I have never seen above 1200 with 7x.010's, a TST Comp and just short of 60 psi.  Weight is 6k lbs...a little lighter than your average 2500 4x4.  I'm looking at upgrading to 7x.012's or 7x.013's since I have some upside egt's. 

[kzimmer]

40 minutes ago, Bullet said:

I have never seen above 1200 with 7x.010's, a TST Comp and just short of 60 psi.  Weight is 6k lbs...a little lighter than your average 2500 4x4.  I'm looking at upgrading to 7x.012's or 7x.013's since I have some upside egt's. 

That's a crazy low temp at 60 psi, I'd love to keep it that cool. How much boost would you see from your primary at 60 psi overall?

 

Tomorrow after I replace my alternator and passenger side mirror, and install my eBay power mirror switch to get power mirrors, if I have enough time I might fix my exhaust drive pressure gauge and do some tinkering with the wastegate and see where I'm at. The last time I messed around with it I never checked drive pressure. Just boost overall vs primary. 

Edited November 23, 2019 by kzimmer

[AH64ID]

On 11/16/2019 at 8:31 AM, kzimmer said:

Those of you with compound turbos, what are you seeing for exhaust temperature at full throttle? At what point do you stop adding fuel and just accept the fact that you are out of air? Not concerned about drive pressure or turbo sizes at the moment, just exhaust temperature.

 

For example, With DAP 7x.013 VCO nozzles set to pop around 315 Bar, with Max canbus fuel command and 1200us of wiretap, I'm seeing a peak of about 1355°F EGT at just over 60 psi. Without the wiretap, It's less than 1200° at 50 psi or so. Is it worth adding a little more wiretap?

Assuming those are non-towing EGTs id say you’re doing well. You may have room for a little more fuel, but personally I wouldn’t touch it. 
 

Ive always liked a peak of 1350-1400 for non-towing WOT runs on a max effort tune. Sure plenty of guys run hotter, but hotter is where you play the game of chances with your pistons. 

[Bullet]

4 hours ago, kzimmer said:

That's a crazy low temp at 60 psi, I'd love to keep it that cool. How much boost would you see from your primary at 60 psi overall?

 

Tomorrow after I replace my alternator and passenger side mirror, and install my eBay power mirror switch to get power mirrors, if I have enough time I might fix my exhaust drive pressure gauge and do some tinkering with the wastegate and see where I'm at. The last time I messed around with it I never checked drive pressure. Just boost overall vs primary. 

I don't have a drive pressure gauge or separate boost gauges...wish I did.  So I don't know how much of it is from the primary vs overall.

 

Your injectors are way bigger than mine so you're gonna be hotter.  I imagine when I get some injectors similar size as yours we'll be more similar egts. 

[kzimmer]

Alright... So I got my drive pressure gauge working. My drive pressure was like 80 psi with primary boost around 20 psi and 50 psi overall, for a pressure ratio of 1.6:1. A little too high for my liking. EGT around 1250°F. That was with no wiretap. Loosened my little eBay boost controller (spring loaded check valve in line with boost reference hose to HX35 wastegate actuator) just about as loose as it would go. Where I'm sitting now, with about 600μs of wiretap, (1200 dividing into two levels), is about 60 psi overall, 30psi from the primary, 85 psi drive pressure, and EGT around 1460°F. So my PR only reduced to about 1.4:1, and my exhaust temp is obviously heating up a little.

 

I'm not sure where to go from here. On one hand, it makes sense that the EGT is going up because I'm opening the secondary's wastegate earlier. On the other hand, one would expect EGT to drop a little when reducing drive pressure. I'm guessing the exhaust housing in this HT60 isn't sized properly. I don't know what it is and I have no way to find out. Doesn't matter anyway, I have what I have.

 

My question is, what's better/worse: 1250° EGT with high-ish drive pressure at WOT, or 1450° with slightly lower drive pressure?

 

Edit: Did another "after adjustment" run without wiretap just for continuity sake. Approximately 50psi overall, 25psi primary, 70psi drive pressure, 1385 EGT. 1.4:1 ish PR.

Edited November 23, 2019 by kzimmer

[kzimmer]

I think I'm going to switch to an adjustable spring gate on the HX35 so it operates entirely on exhaust drive pressure. I'm curious on how much it might improve adjustability.

[AH64ID]

Looking at the different pressures you're making, taking into account the elevation of Regina, you are working the primary harder than the secondary.. which we expect with a loose WG on the HX35. 

 

Your last test has the primary working at 2.8:1 and the secondary at 1.6:1, which shifted from your initial ratios of 2.5:1 and 1.9:1 respectively. You're in the fat part of the compressor map at 2.8:1 on the HT60. 

 

As you can see working the primary harder has good results on drive pressure. 1.4:1 isn't anything i'd worry about. The HX35 is probably going to keep you around that ratio unless you get an external WG and then the benefits are likely not worth the cost. 

[kzimmer]

9 hours ago, AH64ID said:

As you can see working the primary harder has good results on drive pressure. 1.4:1 isn't anything i'd worry about. The HX35 is probably going to keep you around that ratio unless you get an external WG and then the benefits are likely not worth the cost. 

 

Makes sense, thank you for your response. I previously (a couple years ago) opened up the gate hole a little bit on the HX35 and drilled through the other side, and I'm using a non-separated spacer before the HX35. There's not much else I can do other than taking the turbo off again and widening the holes even more, requiring a bigger puck.

 

I'll report back here when I get the spring gate installed. I'm slightly embarrassed to say that I just overpaid for one from DAP made by Crazy Carl instead of making my own. Not a lot of time to do that kind of fabricating and testing right now.

[kzimmer]

Removed the HX35 factory boost referenced wastegate actuator today and installed the Crazy Carl's spring gate actuator. It wasn't exactly a bolt on replacement; the threaded actuator rod it came with and the angle of the spring cup were not angled properly at all.

 

I tried clocking the center section a little to help straighten it out, but I couldn't go any further as my oil drain was hitting the T3 mount on the manifold. So I had to bend the hell out of it and drill out the hole in the bottom of the spring cup larger to accommodate the various angles as the wastegate opens.

 

I had some words, since the only reason I was willing to pay for this thing was so I didn't have to piss around. But, now it's installed... And good riddance to the factory actuator. I can't believe how much this helped. Slapped it on with very little though to spring adjustment, and without wiretap, got 53psi overall, 22 psi out of the secondary, and 55 psi drive pressure at less than 1250°F EGT. Nearly 1:1 DP to Boost ratio from 1.4:1. Primary PR 2.5:1, Secondary PR 1.85:1.

 

Tightened the spring a turn or so, threw on 600ms of wiretap, and saw 60psi overall, 24 psi primary, 70 psi DP, at 1360° max EGT. 2.64:1 Primary PR, 1.93:1 Secondary PR, 1.17:1 DP ratio. I think if I tightened up the spring a little more I could still drop EGT a little and get the PR's on both turbo's a little closer together, but probably at the expense of drive pressure. Might be worth it?

 

Regardless, I'm very happy with the results. I just wish I would have known about it sooner.

 

Disclaimer about EGT measurements: I can't possibly watch EGT while watching three boost gauges. I'm going off of the Max of a WOT run. It's possible that it settles a bit lower, but it's likely accurate.