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Discussion Starter #1
Just wondering when to upgrade hotside. I've got 1 5/8 with 2.5" crossover now. Thinking about Going 1 3/4 with 3in crossover. Looking for 800-900 with s380r on E85.
 

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Discussion Starter #3
Yea idk I just been thinking I need to upgrade. Ive got a drivers side mount kit right now that puts the turbo inlet in the fender and exhaust runs across the front of the motor. Ive just had it dumped near the lower radiator hose. It works good but was thinking with the s380 that I might need to go passanger side.
 

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I've seen cars with 1 1/2 inch primary tube turbo headers run in the 6s in the 1/4. The smaller the primary the more exhaust pulse you get and spools turbo faster. Yes the larger primary and larger crossover can flow more air if not going threw a turbo. Look at the inlet size of the turbo for the exhaust inlet. The housing funnels down to less than 2inch diameter on most turbos. Even 106-118mm only got like 3inch maybe. So think about it you have two 2.5 inch header collectors merging together to go threw a 2 inch hole. Your exhaust is all you will ever need. You want more top end power then get a better flowing A/R exhaust housing for your turbo. Will flow more exhaust threw the turbo and make more top end power but will slow down the spool of the turbo.
 

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You only need larger primary headers if your heads require it for proper unrestricted flow into the header. This is the reason you see large headers on some turbo race cars. It is because the heads that are on the engine have huge exhaust ports and require large primary tubes to flow properly and that is really the only reason. On all other setups like N/A, Nitrious or supercharger setups than primary size and collector size is all important for torque building or bleeding off and for top-end horsepower. This is why Top fuel cars and such have open headers. They are trying to get rid of torque so not to blow the tires off or break the car in half.

Hope this helps.
 

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Very welcome! I sell turbos and components on the side from Precision Turbo. I have decent experience with turbos. Use to hang around the old Pro 5.0 guys and NMRA 10.5 and promod guys like Big Daddy and Job Spettor. Still do when can. Learned a-lot by watching them. Plus years of making lots of mistakes and learning about what worked or didn't. (If want to see some cool turbo setups go on facebook and look up Precision Turbo or Harry Haruska's page. He is the owner of Precision Turbo. Also look on Yellow Bullet and checkout Tim Lynch, Amanda aka (Puddin) and DUCK who run the money drag radial races at SGMP and a lot of stuff on Yellow Bullet. Puddin drives the blue 2005 mustang drag radial outlaw car. Also for some good videos check out The night the lights went out in Georgia Boost vs No Boost on youtube. Also Shane Stacks videos of his small block chevy 1985 red monte-carlo SS.
 

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I still run 1 5/8 and 2.5 inch crossover, made over 925 rwp.

Smaller piping builds velocity resulting in faster spool....it is all good until it becomes restrictive and creates back pressure.

I don't intend to change mine, it seems to work well.

Brian uses 3 inch cross over and 1 3/4 on some of the larger turbo kits he makes but because mine was an incrementally modified stage 1 kit I have the smaller piping.

Sounds like everyone is giving you the same commentary...for once an agreement around here!
 

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This goes way back but marsh(sp?)back in the day of Pro 5.0 was making in excess of 1500hp or so with 1 5/8th primaries.
 

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Like stated above, the primary tubes should exactly match the opening of your exhaust ports for turbo cars and you will never have to step up again, unless you change heads and end up with miss matched ports.
 

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Discussion Starter #12
Yea my headers are smaller then my exhaust ports on my Victor jrs side to side but top to bottom the header is bigger.
 

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Any room to port out the flange a bit?
 

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Any room to port out the flange a bit?
What 88mmNotch said. I am using Victor Jrs as well. The 1 5/8 headers should have more than enough material on the flange to port out to match your head. I am running 1 7/8 primary on my Victor Jrs. so you should have plenty to port out the header flange. Only issue is that you may need to reweld the header if port threw the weld. If worried about porting threw the welds then port the flange meeting the head and port at about a 45 degree angle to if nothing else help funnel the flow.
 

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Discussion Starter #16
I'm going to clean it up and remeasure it. Should come close but if I ever get the heads ported I will upgrade.
 

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Discussion Starter #18
Yea my headers have the very thick flanges so I've got pleanty of room. I can weld it back up if I go through no problem.
 
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