Twins vs. Large Single and reliablilty?

[Subman]

for thoes who tow with twins and consider there truck streetable how does it work out?? to much heat?? any down falls??

Don't think anyone answered this. All I can give you is my experience having owned two daily drivers with twins, an LB7 and my current LBZ. There is much less heat, that really is the heart and sole of the twins, lower EGT's. I have a friend with an LBZ with a stock turbo and EFI tow tune, MSRP 4" exhaust. We have about the same size travel trailers, 28' and they weigh within 500 lbs of the same weight, around 8,500 loaded and wet. If we tow up a grade at exactly the same speed using the same tune my egt's will be 200 degrees cooler than his. I have much more power with the same tune do to more air. I can't think of any downfalls for towing. In my opinion twins do not do well on the dyno, for some reason I can never get even close to the boost I can get on the street. On at least two occassions I have dyned (old LB7) in the mid 500's, had dodges hit 100+ more hp than me and absolutely smoke them on the track, not even close. I'm talking half a second. These weren't heavy lifted trucks either. I limit my boost in my LBZ because I don't want to do head gaskets or something worse if I turn up the power too much. I like it right were it is, fun to drive, very streetable, quick and great MPG.

 

[ChevyDieselLLY]

i think thats the great thing about twins, is that you can still tow anything you want yet take it to the track and just kill it. i think it i werent looking at keeping it so i can still pull id have a set of twins real quick.

 

[dmaxlover]

In my opinion twins do not do well on the dyno, for some reason I can never get even close to the boost I can get on the street.

On Huckstorf's Superflo, Jason Otto with his MPI twins was making I believe about 70psi of boost, which ended up being about 820 hp and 1480 ft/lbs. The dyno was loading the trucks extremely hard. A 4th gear sweep was about 10 seconds long.

I agree with you tho Ken, I heard the same thing in the past about people having troubles achieving full boost on the rollers. Ken, what kind of dyno did you run on that gave you the low boost numbers?

 

[jrad12381]

I would but my right foot tends to get heavy and I dont have the cash for an engine build....... and dunno if I have the restraint to detune lol.

I may live vicariously through you for a few more months hahaha.

I take it you are loving yours so far?

Yeah there awesome! I havent been driving my truck much but what I am really excited for is when it comes to towing my boat this summer. The extra 150-175 rwhp will be nice towing.

 

[jrad12381]

Yeah there awesome! I havent been driving my truck much but what I am really excited for is when it comes to towing my boat this summer. The extra 150-175 rwhp will be nice towing.

Also I was worried and still am worried if my engine lets go, but I went with Robs tuning and I feel a bit safer with his very proven track record when it comes to motors holding together.

 

[EDP]

Don't think anyone answered this. All I can give you is my experience having owned two daily drivers with twins, an LB7 and my current LBZ. There is much less heat, that really is the heart and sole of the twins, lower EGT's. I have a friend with an LBZ with a stock turbo and EFI tow tune, MSRP 4" exhaust. We have about the same size travel trailers, 28' and they weigh within 500 lbs of the same weight, around 8,500 loaded and wet. If we tow up a grade at exactly the same speed using the same tune my egt's will be 200 degrees cooler than his. I have much more power with the same tune do to more air. I can't think of any downfalls for towing. In my opinion twins do not do well on the dyno, for some reason I can never get even close to the boost I can get on the street. On at least two occassions I have dyned (old LB7) in the mid 500's, had dodges hit 100+ more hp than me and absolutely smoke them on the track, not even close. I'm talking half a second. These weren't heavy lifted trucks either. I limit my boost in my LBZ because I don't want to do head gaskets or something worse if I turn up the power too much. I like it right were it is, fun to drive, very streetable, quick and great MPG.

Another reason why we are in the process of developing a Supercharger with a Big single setup on the duramax.

Much more manageable drive pressure concerns, EGT's, and daily driving characteristics.

 

[VABRacing]

Keep in mind, you should never have more than 1:1 drive pressure ratio on a compound setup. Compounds are much easier to manage that ratio as well as streetability. The upside to compounds is much less heat, driveability, and a broader efficiency range. Rather than running a single gt42 at say 55psi of boost. you can now run the same boost numbers and move a lot more volume of air due to a large atmosphere charger say a gt47. Thats the whole idea, moving a lot more air at a given psi.

 

[RENODMAX]

Another reason why we are in the process of developing a Supercharger with a Big single setup on the duramax.

Much more manageable drive pressure concerns, EGT's, and daily driving characteristics.

Mick did this quite a while ago...

 

[racinmike77]

Mick did this quite a while ago...

x2 made a few pounds of boost at idle iirc

 

[Killerbee]

The best turbo compressors are 80% efficient, give or take. If you must compress the air twice, it would be 80% x 80% or 64% peak efficiency.

But let's say you want 75psi air. No single compressor we have access to is more than perhaps 50% efficient at that pressure, probably lower. But you could target a compound setup at 75psi and be 64%.

at first it seems unfathomable that this could be correct, but for series configured twins, it is. High flow rates cost. The magic of twins is the lower PR each can run at, hence higher efficiency.

Given equal technology optomized twins will always have a higher aggregate efficiency than a large single, each capable of the same high flow rate. IMO, a-a intercooling should take place after stage 1, programmable chemical intercooling before/after stage 2. Just a thought.

EGT and drive pressure always decreases whenever you increase compression efficiency. This is a fact made possible by virtue of the shaft connection between each thermo process. The energy required to compress, must be supplied by the turbine. When eff lowers, that energy (by definition) goes up.

 

[EDP]

Mick did this quite a while ago...

Yes he did and we have talked to him about different setups. We are looking to produce a kit that can be sold and is a drop in replacement setup, that does not need any major modifications done to the kit after purchase.

x2 made a few pounds of boost at idle iirc

Boost numbers are controlled by pulley sizes Buddy's 7.3 creates 0 psi at idle.