I’m new to turbos but have been doing a tremendous amount of research and have some questions on my plan.

The goal: The engine is going into a dedicated race car, reliability is the only goal.

The engine: Audi 4.2l ABZ engine, popular choice for turbo builds. It’s a strong motor, has piston squirters and has been used on several 1,000+hp builds with stock internals.

the plan:

exhaust manifold: I’ve heard Long equal length headers will decrease detonation risk so I’m going to an extreme and using long jet boat headers (please see image below) to try and maximize this benefit. I know that I’ll increase lag but I’m hoping the air to water intercooler I’m using with about two feet of piping total will help compensate for this. (First question, there isn’t a lot of research of long tube turbo manifolds, is there something I’m not thinking of?)

Intercooler: as stated above I’m planning on using a air to water intercooler. This is a track car so heat manage is key. I’m using the planning on using the biggest cooler I can find, it’s for 1,500hp+ applications but the pressure drop with liquid to air is supposed to be 1/20th of an air to air cooler so I’m assuming there isn’t much of a penalty for going big (is this true?). I’m using two large radiators to cool the water.
Turbo selection: I wanted to use EFR turbos but man they are pricey! So I’m using twin Borg Werner S200SX Turbos (please see the compressor map below, am I on the right track)?

Other cooling: I’m using three radiators to cool the motor, probably 2x what I need and am using a huge oil cooler with an accusump. I’m planning on using a separate oil and coolant system for the turbos.

All of this should net 640hp which hopefully is reliable. What do you guys think? Any feedback?

cheers,
Stu

#ad


#ad

 

If you mean drag race, track only, go with an ice tank for the A/W. A bit more maintenaince , ice cost, but keeps the IATs way cool and just makes the motor happy and more power.
I dont see reason to separate everything for the turbos. If you going overboard on engine cooling, let that do the work. IMO.

As for the long tubes increasing detonation resistance, I would like to hear the theory behind that.
Backpressure is most likely the issue with that. That comes down to turbine size, and valve timing events be considered during the build.

 

Never heard of using long tube headers on a turbo to reduce detonation. That doesn’t make much sense. It might slow boost response a little. Why not save some money and use stock manifolds and fab up a pipe to connect the turbos it shouldn’t hurt hp. What kind of vehicle is this goin in?

 

I’ll dig up the article on header design. It’s a circuit (road course car) so it has to survive back to back 40 minute sessions in 90 degree heat. It’s demanding on NA cars.

 

ah gotta ya. Yeh you dont want an ice box.

 

You really think headers like that will survive in back to back 40min sessions with all that heat and vibration better than a cast manifold can. If I were you I’d
Be building a hotside outta schedule 40 steel weld els if your gonna take the time fabbing something. The quick and simple way is to flip the stock manifold and put a 90deg pipe on it and add a turbo flange and wastegate flange.

 

I am definitely Concerned about that and my fab guy has the same concerns. He doesn’t think it’s worth making the headers work so more than likely we’ll make headers out of schedule 40 like you mentioned or make the stock manifolds work (which look really restrictive). I can only flip them if I remove the power steering pump which I’m not sure about doing. I’ll almost always be going over a 100mph so it might be OK, especially being mid engine with the weight off the front tires.

 

Schedule 40 seems like the way to go that way you don’t lose the power steering and you can place the turbos exactly where they need to be and the hotside will be very sturdy.

 

One more question for you right now I’m planning on using two Borg Warner SX200sxe turbos which sit in the compressor map nicely. I’m told the EFR turbos are fantastic but twice the price. Does anyone have an experience with them? Could one EFR turbo really outperform two SX turbos? I hear they spool faster but I’m not sure if they spool fast enough to beat a twin turbo setup.

 

Number of turbos has very little to do with spool speed.

EFR turbos are ball bearing turbos, often internally gated, with titanium compressor wheels. They are really designed for race, if you have the money its nice to have. If you setup your combo properly it will probably be good enough without them, most of the time at a road course you can keep the engine somewhere within the turbo's effective range.

 

I should have been more specific. I’m either using one large EFI turbo or two small SX200 turbos. So the smaller turbos should spool fast than a larger turbo, who knows if faster than a single efr turbo

 

In my experience and research, for the same power level a single turbo will spool earlier/faster than equivalent twin turbo's.

Or, conversely, for the same spool a big single turbo will have a higher potential maximum power output.

I'd go single EFR if you can afford it / have enough room for the extra hotside piping.