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Discussion Starter #1
I went from a 84mm to 91mm S400 . Both turbos from Forced Induction .

Just put it on the brake for the first time with the track tune .

Only made 7psi @ 4200 rpm no matter what I put on the gate .

The 84 made 11psi very quickly , the 91 takes twice as long to make 7 psi .

So now I wonder how slow it will be through the eighth mile .

The old turbo made 30psi before the 1 2 shift .

Ive always said street is more important , and its OK on the street but the 84 really spooled much quicker .

I always kept the timing in it and lean on the brake ....... really didnt want to mess with pulling timing adding fuel boost builder crap .


I might have a 91 for sale soon . :unsure:
 

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Boost builder should help. It kinda did for me on my bbc car but i havent finished playing with it.
But on street it may be alot slower to spool. Not much you can do there. Wrap the exhaust to keep heat in maybe
 

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Discussion Starter #3
Im going to mess with the boost builder , but if it isnt much better , this turbo is coming off .

I was very happy with the way it ran before , but was looking for a little more .

I wasnt looking to spend a bunch of time on this though .

Hell , I had this thing down to 1.24 to the sixty and 5.60 to the eighth . Been 8.78 @ 156 ......... Went 8.80 on its last outing .

But I just had to fuck with it !
 

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Discussion Starter #6
I think Ill put the old turbo back on and see how it acts with the new cam .

Just to make sure its not something else .

Because it also seems to struggle more to get up on the converter
 

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I went from an 80/96 to a 91/102 and it’s not anywhere near as bad as what your describing on the street it’s around 500rpms slower to spool then the 80 but at the track on the 2 step it’s within 1 second of the 80 to 11psi it did take more dome psi after the t-brake release to get it to come on quicker but I have it making 25psi in .48 seconds

Give the old turbo a try maybe the new cam is that much different??
 

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If I remember right you have a 12 stator. I wonder if that combo is gonna want a looser converter. I know you pull your boat with it though. I run a 15 and my car is 4200+. I thought mine was tight. I cant imagine a 12.
 

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Discussion Starter #15
I really didnt want to have to spend a lot of time making it work . I was ok with the slower spool on the street , but Im not wanting to spend a lot of track time trying to run 2 tenths quicker .

Sure a 8.50 at 160 mph would be great , but Im OK with what it runs with the 84 .

Plus I have a hunch that it will be slower to get to max boost during the pass also ????
 

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Theres gonna be a difference in 96 turbine and a 104. Also the 91 comp vs an 84.

you will have to try it and find out. Theres more power potential now with the 91/104
 

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Discussion Starter #18
Theres gonna be a difference in 96 turbine and a 104. Also the 91 comp vs an 84.

you will have to try it and find out. Theres more power potential now with the 91/104

I just didnt think it was going to be that big of difference .

Dont get me wrong , I had no problems with the other turbo . It was better on the street anyways .

Just always wanting to go faster I guess

I just wanted to do it with little or no effort .. LOL
 

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I just went through this. switched from a 85/96 to a 91/102 on my 5.3 . the 85 would make boost at 4200 . I had to raise the 2 step rpm to 4600 with the 91. I did a test at 5000 rpm and the boost went to 22 lbs...lol
 

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Discussion Starter #20
Well after pulling that big ass bitch off and I was putting the old one back on . After having everything hooked up and bolted down , I started looking for the oil line and grabbed the nearest -4an line I see .

It was the BOV reference line that wasnt hooked up when I installed the 91 in the first place . WTF

So after I calm down a little , Ill go back out and put the 91 back on and test it .

But not sure why it was still making boost when driving it .

It might be a beast now ......lol
 
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