Twin turbo cross over pipe

[plowboy_lbz]

Right now I have an epr twin kit on my truck. The kit uses a 3" cross over pipe to connect the s475 to the stocker on the intake side. I see other kits use what looks to be a 3.5" or 4" pipe. In my quest for better low end spool would going to the larger piping help? I haven't measured out the v-band outlet on my s475 but it looks to be atleast 3.5". My theory would be that the larger pipe would be easier for the high pressure turbo to suck air through until the low pressure turbo lights, creating less lag.

From a dead stop it spools good (can always be better) but what I'm after is low end spool at cruising speed. I'd like to roll into the throttle and get both turbos to light faster. The only down side to using the larger piping would be fitment. Right now the 3" pipe contacts my profab y-bridge, but kits like WC Fab come in at a different angle, so that might not be a problem. If anyone has some insight it would be appreciated before a spend a couple $100 only to figure out it didn't help any.

 

[IOWA LLY]

It will not make it spool any quicker. I understand your train of thought but the restriction is in the compressor side of the S475. Not the 3" tube.

However, having said that, a 3.5" charge pipe has several advantages over the 3" and is what I prefer to use on a setup like yours. Its up to you if you want to spend the time and money but imo its not going to help with what you want.

If you want to perk up the low rpm spooling you can look at making some changes to the hotpipe. (The exhaust pipe between the turbos) Another thing to play with is vane position and commanded boost at low rpm. Be careful though as to much commanded boost down low will hurt power and fuel economy.

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[plowboy_lbz]

It will not make it spool any quicker. I understand your train of thought but the restriction is in the compressor side of the S475. Not the 3" tube.

However, having said that, a 3.5" charge pipe has several advantages over the 3" and is what I prefer to use on a setup like yours. Its up to you if you want to spend the time and money but imo its not going to help with what you want.

If you want to perk up the low rpm spooling you can look at making some changes to the hotpipe. (The exhaust pipe between the turbos) Another thing to play with is vane position and commanded boost at low rpm. Be careful though as to much commanded boost down low will hurt power and fuel economy.

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Any power advantage up top? Would a race cover help any?

 

[IOWA LLY]

I believe the 3.5" helps throughout the rpm range. I just don't believe you will notice any difference in spool up.

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[plowboy_lbz]

I believe the 3.5" helps throughout the rpm range. I just don't believe you will notice any difference in spool up.

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I'm always up for adding more hp by reducing restrictions.

 

[Chevy1925]

I would look into ways to either a billet/batmowheel for the 475 or upgrade the exhaust side of the stock turbo and the hot pipe like IOWA said. running the ported/poslish stocker from russ made a difference in spool up for my rig till i put the 480 on and it dropped back down again.

 

[countrycorey]

After talking to mark about it, the 475 standard cover is too tight for the valley turbo to effectively breathe through at low rpms


Corey

 

[plowboy_lbz]

I would look into ways to either a billet/batmowheel for the 475 or upgrade the exhaust side of the stock turbo and the hot pipe like IOWA said. running the ported/poslish stocker from russ made a difference in spool up for my rig till i put the 480 on and it dropped back down again.

I would be all for a billet or batmo wheel but everything I've seen is so inconclusive. I don't want to drop $500+ on a wheel that will only make things worse. I'd be more apt to trying a batmo wheel, but you can't buy them outright.

After talking to mark about it, the 475 standard cover is too tight for the valley turbo to effectively breathe through at low rpms

Corey

The answer to that would be what? A race cover? Step up to a s480?

 

[Chevy1925]

A batmowheel/billet in the valley, no I wouldn't do one. The big one is the only one id do.

No a 480 is just a 475 cover milled to a 480. A race cover would be better and I may try that next on my 480 before a wheel

 

[countrycorey]

I would be all for a billet or batmo wheel but everything I've seen is so inconclusive. I don't want to drop $500+ on a wheel that will only make things worse. I'd be more apt to trying a batmo wheel, but you can't buy them outright.



The answer to that would be what? A race cover? Step up to a s480?

You can talk to mark about getting a wheel. Could go either way with that, have to see what will work better for your needs.


Corey

 

[plowboy_lbz]

A batmowheel/billet in the valley, no I wouldn't do one. The big one is the only one id do.

No a 480 is just a 475 cover milled to a 480. A race cover would be better and I may try that next on my 480 before a wheel

You test a wheel and let me know how it works before I buy one. :hug:

You can talk to mark about getting a wheel. Could go either way with that, have to see what will work better for your needs.


Corey

I would really like to get as much power, or I really should say efficiency out of my current set up as I can before adding injectors, NOS, or anything else.

 

[countrycorey]

I would talk to mark, he will be able to get you the answers you're looking for


Corey

 

[MaxPowerLB7]

The earlier kits had 3.5 tubing but the bends needed to be cut so deep to fit it would end up with oblong ends and took considerable effort to straighten out. So they were reduced to 3 inch to reduce fab time and improve asthetics. The outlet on a 475 is 3 inch IIRC as well, the flange is 3 inch or smaller id.

 

[Chevy1925]

You test a wheel and let me know how it works before I buy one. :hug:



I would really like to get as much power, or I really should say efficiency out of my current set up as I can before adding injectors, NOS, or anything else.

Look at cokers thread about swapping his 480 cast to a batmowheel. I'm not saying it's he way to go, I would go with what ever mark suggests. At some point I'll be trying either a wheel or cover though

I noticed a heck of a difference with the reworked stocker and the 480. Top end is stronger and pulls harder through out the whole range.

I wonder if mine is 3.5 or 3.0. It's the original kit off Trent's white truck he built before making the kits.

 

[MaxPowerLB7]

Look at cokers thread about swapping his 480 cast to a batmowheel. I'm not saying it's he way to go, I would go with what ever mark suggests. At some point I'll be trying either a wheel or cover though

I noticed a heck of a difference with the reworked stocker and the 480. Top end is stronger and pulls harder through out the whole range.

I wonder if mine is 3.5 or 3.0. It's the original kit off Trent's white truck he built before making the kits.

Yours is 3.5. Llys-lmms were changed, but lb7s dont really give a choice nor is there issues with tight fitment.

 

[Chevy1925]

Ah thanks Matt!

 

[plowboy_lbz]

What about running a turbine diverter on the big charger? I don't know if they made one to fit a t6 or if it would even be cost effective. But I would think it would help the big charger spool faster which could decrease spool time. Just thinking out loud.

I'd love to try a billet wheel and/or a race cover but damn. It takes what was a $700-800 and turns it into almost a $2,000 turbo.

 

[Dallas S]

What size is your hot pipe?

 

[plowboy_lbz]

What size is your hot pipe?

3". Since the outlet on the stocker is 3" I don't see an advantage to a 3.5" let alone making it fit.

 

[IOWA LLY]

No one said anything about making the hot pipe bigger.....

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