Spent about half hour on the phone today with Dave at HTT. I have been planning on twins, but after considering they might be louder than I want, I decided to see what HTT would recommend for a single for my set up.

Here's some background. The A3k worked great before injectors as far as keeping egts in check both at WOT and towing. Since I have added injectors, it still does a pretty good jog at WOT for no bigger than it is, but towing ability is gone. If I'm on an incline at all, it surges really bad and I have to drop it to 3rd to get the rpms up to stop it.

So in a quest to solve this problem, I made an assumption that twins would take care of this problem. After talking to Dave, he says probably not. he also said that he doesn't have a single that is probably going to give me what I need/want either. Basically I am overspeeding the exhaust wheel of the 3k with the injectors. He said I would need to go to a turbo with a larger exhaust wheel but then my egts are going to suffer at cruising speed while towing. At a steady cruising rpm the larger wheel won't be driving the compressor wheel and I won't be building any boost and so the egts will run up. He said the first thing he would try at this point would be to upgrade the IC so that it isn't holding back what the A3k is pushing during the overspeed condition.

So my question is: what is everyone running for a turbo that tows with 100hp injectors and how does it act and what do your egts do?

 

I talked to Dave the other day as well. I'm in a similar boat as you.My HTT62-12 is great for towing and everyday driving,not so great at the strip.My drive pressures are probably thru the roof at WOT on the strip.My boost will spike to 48-50lbs before falling back to the wastegated setting of 44lbs.Egt's aren't too bad at the strip.In the range of 1450-1550*(on an 1/8 strip,never ran a 1/4). I want the best of both worlds and the only solution seems to be twins. Dave sure doesn't like twins for towingI dont know why. I talked with Nathan at MPI and there are different combo's he feels will spool near as quick as a single and have some top end also.He was pushing the GT42 for the bottom turbo because he said it spools quicker than an S400 and it is wastegated.Not as muck hp as the S400 but definitely better for towing.Only good for around 600hp with the GT42 but thats about all I want.

 

But according to Dave, I would still be overspeeding the small turbo, be it the A3k, a 62/12, or a stocker and would still have the same surging problem I have now. It seems like there has to be a solution, because there are too many guys in the 600hp range with injectors that still tow on a regular basis.

 

Alot of people tow with large singles but driving habits have to change.Us straight drive guys have it better for controling surging than autos do. My friend is running a 64/71/13 with a 6 speed and he tows but it is annoying having to watch what gear and rpm your at trying to avoid surging.when hes climbing a grade is when its worse and thats when you want all this power to work the best.His cruising egt's are about 200* higher than mine at the same speed pulling roughly the same weight. I want quick spool and good top end while maintaining good egt's when towing.If i'm going to have to relearn how to drive I'll just stick with my current set-up.Call Nathan and talk to him.He's really sharp on this stuff and won't sugar coat it for you.If you tell him what you want and its not possible then he will tell you,not try and sell you something you wont be happy with.

 

The small turbo would not be overspooling because it will be wastegated at a much lower psi.

 

My towing experience has only been with the towing twins from BD. Holiday trailer 8-9k, very long grades 80mph egts 1150f. Drive pressure at that point in time would have been 1:1.
The combo was flux 3.5's, Smarty on a lower setting, intercooler, and stage 2 pump. I have a six speed, I used 5th on most hills and sometimes on flat grade...however I do run 37" tires. To me you cannot go wrong with a small set of twins. The BD twins are not too loud, I would recommend going for a shotgun ride with a member close by.
You need to condsider your ultimate wish and buy based on that. If you want to tow and street rod OK if you want to tow and race not OK.
The more fuel you feed the smaller turbos the more issues you will encounter with drive pressures, egts and max power.

onetun

 

Actually Dave did say the the BD towing twins might work for towing but that they wouldn't support my fueling well. Sounds like I'm kinda stuck here.

 

Except then I'd be back to the situation of having high cruising egts due to lack of air because the wastegate is dumping.

 

Take a deep breath!!! In-- out-- ahhh....

Hey the answer is right there above. Look the twins I have are super for towing with high HP. No surge at all, no barking at all, not really loud and and I have posted here before, basically towing 10k up a 7 percent grade, in 104* weather, at high elevation (between 3500-6500ft) using all of about 450HP doing it, egts never went higher than 1350 briefly and was mostly around 1100. That said, I have a good friend with an '06, 48re, 100hp DDPs, BD towing twins, running Smarty/TST stack and tows his 12k fifth wheel between California to Washington here and there and never has a problem at all and has been getting good fuel mileage too. His twins are not loud at all either. His stacks can be though. In any case he doesn't see egts over 1250 according to him and can still push 70 psi too. There is no bark, no surge at all and those things are very responsive too... twins are definitely your solution. As far as noise goes, singles are always louder than twins. The twins have a way of canceling out noise almost like having another or a better muffler back there. You will get some whistle, but it will be that way with any turbo without a silencer ring.

 

I don't know Dave at HTT, but I have to think you are not getting the best advise. I'm not going to bash him here, but rather I invite you to talk to people like those at BD, or Nathan from MPI or Piers Harry or even II. Talk to them that have direct experience with the twins. I will tell you that I tow extensively with mine and just like going from a gas engine to a diesel, there is that much a difference in going from a single to twins and I won't go back to a single turbo or a gasser. The downside to twins are the expense and the initial tuning/setup and installation. Once in and dialed though... look out!

Ask Shane (luvnacumns) about going from an A5k to MPI twins how he felt about it!

 

I have to tell ya, the BD's (and understand I am not pushing their product, but rather addressing the question) will support your fueling. They do well up to 600+hp, and the new twins will support 700+hp.

Maybe Kantdrive55 will see this and chime in to help explain better for his product... or others for the other twins out there, but you can definitely have your cake and eat it too.

 

That's exactly what I need to do right now - deep breathing. I am still trying to get a hold of Nathan to talk to him about this whole ordeal.

So do you have an aftermarket intercooler? Also, do you have an external wastegate?

Thanks for the info too.

 

I do not have an aftermarket intercooler nor an external wastegate. For the power I am making now, I really don't need either. For the power you can make, the intercooler may be useful, but not mandatory by any means. The external wastegate will depend upon a lot of other factors. But when towing, you can't really use the power you are capable of 650hp-- you will have to detune to a degree. The limiting factor becomes your engine cooling system.

 

oma your dyno numbers are pretty strong with a A3
With respect to fueling, I see no issues.
I do not think you will over fuel the towing twins from BD, I also don't believe you can make over 580 with the twins and your fueling mods. Someone may be able to make 600 on #2 with the BD twins but I have never seen a thread of graph providing that information.
Understand the rating of the turbos from any manufacture is "up to" and longevity needs to be considered. If you are going to constantly push the limits parts will break.
I run a BD cast aluminum intercooler..not sure if it is on the public market. This cooler much stronger and should hold 100psi...

onetun

 

Any one have any experience with using a GT42 for the bottom turbo? Nathan said this turbo was much more suited for towing applications.