I was not under boost in that screen shot, just normal cruise. E85 is around, but not everywhere. The only thing I am afraid of is getting out and need fuel and not being able to find it.

 

Was doing some test and tune this weekend. Looks like my wastegate is too small, was getting 5-7 pounds boost with no spring in the gate. Also have about 15 or so pounds drive pressure with about 5-6 pounds boost. So I need a larger gate. I thought about going from the .91 AR to the 1.00 AR exhaust housing if that would help drive pressure. Or, should I upgrade to the S472 with the T4 housing? Really dont want to spend a grand on another turbo if I dont have to.

 

The drive pressure is more turbine related than wg. As long as you can regulate boost to your desired level, the gate may be marginal, but is large enough, and a larger gate will allow you to run less boost, but won't do much for your drive pressure. The switch from a .91 to a 1.00 would be a waste of money imo, and a larger turbine is needed for your current setup. The 83mm turbine hardly seems like an upgrade, so the 87mm is looking pretty good.

 

For some reason the picture of the IAT sensor isnt showing up for me....cant help you there.

IMHO another culprit for your high backpressure is the compressor (turbine as well, so the entire turbo) is too small for the application....requiring more power to produce the required mass flow rate at the current pressure....of course this power comes from flow work (enthalpy) in the form of a pressure and heat difference across the turbine. That turbo is a good start for a ~250 hp N/A engine (guessing I dont have the map in front of me)....not a modified stroker V8 (guessing ~400 for NA power).

 

This was the discussion originally, and now the engine in question has more cam, and head flow than the original iirc.

 

thus making the problem worse

sorry i didnt remember that from reading it originally awhile back.

 

No worries, didn't mean anything by it, just agreeing.

 

Well guys, took the truck out again the other night. Gave it a little more timing and leaned her out from 11:1 AFR to 11.5:1 AFR. She came alive and pulled hard on 8 pounds, still no spring in the gate. I am not getting any knock under boost, MAT was reading about 89 degrees F. It was a pretty cool night.

I hooked a better gauge up to my exhaust, my old boost gauge, and was able to get a more accurate reading on back pressure. Looks like I am more like 8 pounds of boost with 15 pounds back pressure. 1.9:1 ratio. Its hard to watch both gauges while doing 80 MPH....LOL. I need to get someone to ride with me to watch a gauge.

Don't flame on me too hard but I am thinking about just throwing an Ebay GT45 on there. I have read the 90+ page thread on them. I think it will do what I want. With a 69 mm compressor and a 87 mm turbine 1.05 AR exhaust housing. I really don't want to spend a grand on an S472 right now. I am also upgrading my waste gate to a 50 mm Tial.

I still want this thing to came on early and pull hard to 5000 RPM. Thats really all I care about, I do not want to loose my mid-range torque.

 

A boost to bp ratio of less than 2:1 is workable for the power, and rpm you're after, I expected it to be higher than that. Nothing wrong with the gt45 for the price.

 

Just did the calculations on this turbo, as far as the compressor. At 66 lb/min, 2 pressure ratio, 12.6 lbs boost, at 5000 RPM, I come up with 600 HP at the crank. That's assuming VE is 95% on this new engine.

Should run way better, considering I will be dropping back pressure on the exhaust as well.

 

Just do the billet wheel upgrade. An 88 ar open housing would reduce back pressure over the 91 divided. 2:1 isn't bad for a rig like yours. Can you log ve? I'd like to see a screen shot of the curve under full boost conditions. Ford has engine load parameter and is very informative on turbo cars.

 

What turbine wheel is in that turbo? 68mm or 74mm .

 

And yes looking at your gate it's way small on a turbine that small as a single on 383 . If you want to run a small turbine for spool you need big gate to run up top or gates add one more of what you have if it's cheaper than a 60 is mm at this point.

 

66 mm compressor, 80 mm turbine .91 AR housing.

What about a 44 mm Tial gate? That's going from 1.5 "to 1.75".

 

Ok so you have the box s366 80-74 turbine. 44mm gate might work but probably not going to be enough for the rpm you are turning.

 

Ok my math is not the common way people do this but it's what I know that turbine will flow around 400 cfm that has nothing to do with pressure but it gives you a volume to work with. Now take your basic volumetric mathematics of your displacement. Short answer is that turbo will take you to rufly 3600 rpm non gated . Now you need to gate big enough to flow the difference in the rpm you want to run at wide open . To go to 6000 rpm you need an additional 265 cfm of flow from your gate. Now scfm comes in to play let's say you want 10 psi of boost and assume 2 to 1 drive to boost meaning you need a pipe to flow at least 265 scfm at 20 psi. A 2" pipe is rated 215 scfm at 20 psi. A 2.5" pipe is rated 350 scfm at 20 psi. Meaning that's what you need a single 60 mm gate .or two 1.25" at 135 scfm (32mm) gates . Hope this helps.

 

I have the truck shifting WOT at 5000 RPM.

That's why I am thinking about the Ebay GT45 now, with the bigger turbine and exhaust housing, that should lower my drive pressure. I researched the effects of drive pressure, and from what I have read its always a good thing to lower your drive pressure.

 

That s not available for my turbo. Thats for the 76mm wheel, I have the 80 mm turbine. But I can go to the 1.00 AR Twin housing for the 80 mm wheel.

What billet wheel are you talking about. I looked into that, I found the Wicked Wheel 2 that a lot of diesel guys use. Or this one?

http://www.ebay.com/itm/like/111328902177?lpid=82&chn=ps

I have the BW 177275

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They make a 1.10 AR housing for the 366 as well it was used on dt 530 up grade turbo. It has a longer down pipe snout tho . But the wheel is the restriction still . The e-bay gt45 isn't the answer in my opinion the cold side is bigger but the hot side isn't by much just going to be lazier than the 366. you built a killer setup that works has good parts you just undersized your gate. No need to revamp the turbo just to get around the gate . The 366 can make 700+ at the wheels I've seen it happen.

 

I'm sure it can support 700+ at the wheels, but not on a 383 that makes some decent hp na. I'm curious why the need for a 60mm gate.... The fact that he makes 7psi without a spring means he needs a larger gate if he wants lower than 7psi, but isn't backpressure going to be the same with a 38, or a 60mm at the same boost level? The wastegate bleeds off enough pre-turbine exh to maintain a given boost level... it takes a given amount amount of exh flow (and thus pressure) to create the same boost level regardless of wastegate size, and the larger gate will just be open less.