Longtubes can scavenge better than stock and have less turbulence, and thats separate from temperature differences. I would not compare that as apples to apples of a turbine. The less vacuum you have a cruise the more efficient you are.....which can be accomplished either with a compressor change or turbine change.

 

Yea man you are right. I’ve seen some funny **** on here where people thing they can slap a turbo or blower on with a handheld tuner and think that’s going to work. Or no tune at all. Lol.

but yea, I’ve done what I can to maximize my tuning. I really feel like the exhaust is choked up. It has no ***** until it’s just getting into boost. It just feels choked. You’d think the wheel isn’t restricting it but when things aren’t being forced out, it may be a little restricted.

 

Did they change to a divided manifold as well? I am thinking about replacing my cast vs7875 with a divided t4 s480.

 

Well I lost focus of this endeavor. but now i'm back considering it. I'm re-building a complete exhaust system for it this time out of 3.5" pipe. The 3" just isnt cutting it for me anymore. While I do that, I might as well change the exhaust housing. I talked to viren and he can sell me a housing to fit my turbo that has a 1.25 AR and a 3.5" outlet. I think that and a 3.5" exhaust so flow a good bit better. The bad thing is the difference between the two housings wont be able to be compared because I'll have a completely revamped exhaust at the same time. I dont have any dyno number or track numbers with this motor either.

 

Thread resurrection. I bought the 1.25 housing quite a while back. And I haven’t had time to fool with it. I got a wild hair yesterday and started cutting pipe for it and jacked up the car to start taking it apart. I’m still nervous about losing my excellent spool I have not. She comes into boost quickly and not abrupt. I hope I don’t mess that up. Here’s a couple pics as I work on getting ready to start cutting up the original down pipe

 

Jesus. Look at the size difference!

 

Housing mounted. I’m cutting and welding the down pipe right now

 

I’m fighting getting the downpipe to fit

 

Got it done. Test fit everything and it’s good. Cranked it and it actually sounds better. I gotta pull the down pipe back off and wrap it.

 

Looks good. Curious on the results.

 

Looks good, the 1.25's are girthy units! I had good luck with them.

 

i know. I sure didn’t think it was going to fit and I almost put the car back together. I even marked the down pipe where I cut it just in case it didn’t work out. I’ve gotta go pull it back apart and wrap it. It’s a shame because I love the way the pie cuts look.

 

Aight. Went for a test drive. Lag seems about 500rpm more. Not too bad. For some reason it didn’t really pick up any boost. It is 82f today and it’s running better than it does in cold weather. It spins noticeably more in second for a 60 roll. When I go to third it definitely pulls harder. Cruising around and giving it a little more than than cruise, it doesn’t come into boost as easily. Which is kind of a plus because sometimes when I’d want to speed up, it would go into boost when I didn’t want it to. Worthwhile swap? Probably. It definitely has more power.

 

O I forgot to mention. The engine is more responsive out of boost and it doesn’t sound so choked up.

rode around for a bit. I do drive this car a lot so I’m pretty in tune to how it feels, sounds, responds etc…

so like I said above, it’s more responsive out of boost. Which I didn’t expect. But it’s definitely a welcome result. Car is quieter. Really don’t know why. It’s smoother. Do know why either. I think I had a small exhaust leak before that I didn’t realize I had. Must have fixed that. Learned a new trick for v bands is probably why. I thought to myself, why not put some anti seize in the clamp so it’ll have less friction squeezing it. That seemed to help. Definitely.
it does come into boost fairly quickly. I say fairly because with the other housing on, it was “almost” n/a quick. By the time my foot was to the floor, it was in boost. Now it has a tiny delay and honestly I expected the boost to be more abrupt. My buddy has a 5.3 in a Silverado with a precision 7875 and it’s like a light switch. His seems to have more lag last time I drove it.

Now for the part that most of you dont care about. Some might.
my idle sounds better. Before it sounded like it was kinda struggling. Now it sounds smoother. For lack of a better way to describe. The fuel consumption at idle would always be .82-.90 gal per hour and it would fluctuate a lot. No explanation for that. No tune change yet. And now it idles still .78gal per hour. Not a huge difference by any means, but a difference. The coolant temp also seems lower. It never got over 190 and I made more than half a dozen wot rips back to back. Run it up to 120-130 and let out. It would usually see 200 even in 75f weather. Temps came back to 182 very quickly. Why? Maybe that other housing was keeping some excessive heat in the motor?
also at a 55-60mph cruise, fuel consumption was usually 22.5mpg but now it’s at 24.5mpg. Maybe a coincidence? Maybe the exhaust leak? Maybe a placebo effect? I do constantly look at it, so that’s what it usually is.

 

One last pic and a question. Do you guys think I could add another degree of timing on the higher rpm range? Like past the torque peak. Right now I have it at 11 degrees pretty much straight across. Still on pump 93 with a 5gph nozzle shooting washer fluid past 15psi.

 

I'd read some plugs.

 

I looked in my tune, I had already ramped it to 12. I’m gonna leave it where it is.

 

I always ramp timing down to peak torque and back up to peak rpm. Fuel burn rates stay nearly the same, so peak cylinder pressures will arrive too late for maximum power if you do not add timing as rpm increases. You need a lot more timing at 7krpm than 4krpm. You can also lower EGTs and make life easier on your turbo with higher timing at higher rpm.

 

Brain fart. So I was wondering why my boost was about 2 psi lower. So for some reason I was thinking if I freed up flow, I should pick up boost. Yea, opposite on the exhaust side. I was telling my buddy I thought I had a exhaust leak at the wastegate. That’s why the boost might be lower. He agreed at first. Then it registered. He reminded me that if I freed up back pressure, boost will be lower. Doh. Lol. Not sure what I was thinking. So I just added some more spring pressure to the gate so it’ll hopefully go back to 20-22psi.

 

Wouldn't the boost controller make up the difference based on what the back pressure is? The only way you wouldnt reach the target boost is if you had so much back pressure that the controller and springs couldn't overcome it.