Twin turbo a small block... settle an arguement, good or bad

[Flatty]

I was arguing with a buddy last night about this. so I turn to the powers of PBB. In a rockcrawling application, would it be beneficial to twin turbo a smallblock. Now I can imagine on the lakebed, where the speed is a good thing, then yea, but on the rocs, the SB chevy has plenty of power. There would not be a need to put that kiond of power to the ground. Am I wrong here, or is it a beneficial thing?

Dima

[K5runner@hotmail.com]

Don't be stupid, everyone know that little blocks don't make power. If you want power 632 twin turbo BBC.

[73FJBUGGY]

Obviously this will just be everyone's opinions...but if slower, technical, rockcrawling is your bag...then the turbo setup is useless...in fact a hinderence. Turbo engines typically run low compression to allow for the extra compression when the forced induction kicks in...so if you don't stay in the high RPM range all the time....then you will not take advantage of the turbo power. You will just have a regular low compression motor.

A supercharger is better since it is belt driven, but once again is dependent on your wheeling style. Very useful in the rockbouncing and go fast world for example. I prefer a naturally aspirated enging that makes its power from high compression or displacement, but a superchager setup like Woodlees blower buggy makes sense for the right application. My .02

[toyworx]

http://www.hotrod.com/techarticles/h...g_bang_theory/

[gnob]

it depends on the setup and where the boost comes on.
there are variable turbos that boost across the band.

the reason porsche went from a single turbo in the 70s to a twin was for a more linear powerband. not a switch.

would i recommend it, no. can it be done correctly and usefully, yes.

[85blue4runner]

IMO, a twin (sequential) turbo configuration on a gasser, especially import or high revving engines, is a great idea. Wonder why more people dont do it.

The diesel guys have it all figured out, so why not learn from them? A small block makes almost no power down low, so you need a small turbo to start building boost right off idle. With a V8, there is plenty of exhaust pressure and volume to do this easily. You should be able to start building boost around 1500-1800 rpm depending on the turbo. Then use that turbo to light a larger one in the 3000-3500 rpm range and run it until it gasses out at 6k or whatever your redline is.

No boost lag, smooth even power all the way through the rpm range and much more efficient than a belt driven blower. Small turbos like a Mitsubishi 16g can be had very inexpensively. Talk to someone who builds twins and know how to size them, do all the piping properly etc and you will have a nice system for almost any motor.

.02

[HeyBeerMan]

I would go with multi stage NOS. A onefitty shot that kicks in at 1/4 throttle. Then stack another twofitty shot that kicks in at 1/2 throttle.

Best of all worlds. You can go right from rock crawling to sand drags.

Or just build a healthy smallblock and have all the HP you need. I disagree that a SBC can't make good useable lowend.

Blake

[stjjames]

Originally Posted by 85blue4runner

IMO, a twin (sequential) turbo configuration on a gasser, especially import or high revving engines, is a great idea. Wonder why more people dont do it.

The diesel guys have it all figured out, so why not learn from them? A small block makes almost no power down low, so you need a small turbo to start building boost right off idle. With a V8, there is plenty of exhaust pressure and volume to do this easily. You should be able to start building boost around 1500-1800 rpm depending on the turbo. Then use that turbo to light a larger one in the 3000-3500 rpm range and run it until it gasses out at 6k or whatever your redline is.

No boost lag, smooth even power all the way through the rpm range and much more efficient than a belt driven blower. Small turbos like a Mitsubishi 16g can be had very inexpensively. Talk to someone who builds twins and know how to size them, do all the piping properly etc and you will have a nice system for almost any motor.

.02

This.
I've been toying with the idea of TT'ing my 5.2. I figure using two, same sized turbos (essentially just turbo'ing each engine bank) with the proper sized impeller, I can be at full boost under 2k & kill it at 5500rpm. In stock form I make max torque at 3K & HP at 5K - the turbo's would compliment this perfectly - smooth, linear, unobtrusive power. I just wanna make my V8 air pump work more efficiently.
Besides, I can build a turbo kit, a superchargers out of my price range.

[laproscopic]

I turbod my lexus crawler and wheel it hard. turbo is useless and can make wheeling technical situations tricky. if you have an automatic and dont have deep gears the turbo can be anoying.

case in point:
immagine a situation where you are loading the torque converter on a steep technical waterfall. you dont have real deep gears so you must load the converter somewhat. to load the converter you must rev the motor. this motor load starts to spin the turbo and build boost. to get over the crest of the waterfall you need a little more power so you give it a little more gas. then right as you are about to crest the lip in the waterfall the boost gets to a point where the motor is making power in a non linear manner. this extra boosted power loads the torque converter quickly and the truck lurches forward and you dont have control of the situation.

once i put lower gears and tcase in my rig it wasnt as much of an issue.

[braxton357]

Originally Posted by stjjames

This.
I've been toying with the idea of TT'ing my 5.2. I figure using two, same sized turbos (essentially just turbo'ing each engine bank) with the proper sized impeller, I can be at full boost under 2k & kill it at 5500rpm. In stock form I make max torque at 3K & HP at 5K - the turbo's would compliment this perfectly - smooth, linear, unobtrusive power. I just wanna make my V8 air pump work more efficiently.
Besides, I can build a turbo kit, a superchargers out of my price range.

He's talking sequential twins, quite a bit different than what you're talking about with parallel turbachargers. And, as long as we are talking about an sbc then you really couldn't go wrong depending on how much power you want to make. Build a typical forged 10:1 with a turbo cam then run a single with low boost and have the same low end torque as any built 350 but twice the power up top. If you can't drive a high hp rig then you can't drive a high hp rig, it's not like this is any different than the high horse motors that don't make any power until 3500 rpm. Adjust your stall speed accordingly.

[FORDTECHGURU]

exactly, turbos will boost by load, holding throttle steady and starting to climb a hill they will spool and accellerate, not ideal in a technical situation... now for sand...

[JPI Motorsports]

I have a bunch of experience with turbos and twins in the drag racing world so here's a quarters worth of info.
With the advancements in turbo boost controlers and tuning software, ie: Fast XFI and Big Stuff 3, Boost now a days is almost instantanious. More times than not, we are pulling boost out of the cars at low speed and rpm just to get the car to hook.
laproscopic gave a good example of a problem with turbos, but with digital boost, fuel and timing controlers, this can be eliminated pretty easy.
beerman, please don't tell people to hit thier motor with a 150hp shot at 1/4 throttle. N2O is a safe power adder but only at WOT with enough timing pulled out to keep the tops of your pistons in one piece. I started out N2O racing about 15-20 yrs ago and have more burnt pistons than I care to. I know there's an esception to every rule, but unless you have stock in TRW, Mahle, or JE, don't hit the little red button unless your foot is on the floor. At the very least, if the motor lives, a 150 hit at 1/4 throttle will just make the motor cough, sputter and die..
As far as turbos needing low compression, well it depends on what kind of fuel you can afford to run..We ran upwards of 12-13.5:1 with a single 106mm Precision turbo on a 347CID Ford motor with 30+lbs of boost runing VP C23 race fuel, but at $23 a gallon retail, wheeling with it would be crazy. 9.5:1 with super unleaded and a little extra timing taken out will still make good boost. To build boost quickly, you need a good boost controler and something like a MSD 7531 to control the timing retard, and a tuner that knows what he's doing. To build low end boost, you add fuel and remove timing on the fuel and timing maps in relation to engine RPM and you get cool flames out of the pipes to boot! You can't compare a turbo diesel motor to a gas motor either.
Don't mean to sound like a smart ass, just adding info.

[laproscopic]

modern turbo tech is great but...$$$. Properly sizing a single turbo can be tricky- sizing Large motors (v8 small block) are even harder. Now try and do sequential turbo's and pay for all the electronics to make it work. now add dyno time....
would be cheaper to buy a new crate ecoboost

point is that making one off, powerfull turbos work well in a rock crawler isnt going to happen.

[bbaXJ]

Originally Posted by stjjames

This.
I've been toying with the idea of TT'ing my 5.2. I figure using two, same sized turbos (essentially just turbo'ing each engine bank) with the proper sized impeller, I can be at full boost under 2k & kill it at 5500rpm. In stock form I make max torque at 3K & HP at 5K - the turbo's would compliment this perfectly - smooth, linear, unobtrusive power. I just wanna make my V8 air pump work more efficiently.
Besides, I can build a turbo kit, a superchargers out of my price range.

If you're at full boost at that low of RPM then by the time you hit the top end you'll have more than maxed out the turbo's, be pumping hot air, causing high IATs and EGTs, risking detonation or at a minimum losing efficiency and power, etc. Sequential turbos would be better suited to technical wheeling, but as has been said already, they'll still make things tricky since in many scenarios they'll either boost when you don't want it or not boost fast enough when you do want it. I was building a GM LQ4 6.0L powered Scrambler that I wanted lots of power in. I originally did a ton of research on turbo kits. Even though I was gonna do lots of dune running and street driving it still made more sense to run a supercharger due to the type/timing of power needed. I still would've been better off spending the money to mod the 6.0L to make crazy power all on its own but I wanted something different. You can make any setup work reasonably well, but the best all-around performance for any type of technical wheeling will be to just modify the engine itself to make as much power throughout the RPM range as possible.....the flatter and earlier the torque curve the smoother it'll be, and generally speaking that'll be easier to do on just motor than on a system that relies on the motor spinning compressor wheels, whether they're belt or exhaust driven.

[stjjames]

Originally Posted by braxton357

He's talking sequential twins, quite a bit different than what you're talking about with parallel turbachargers. And, as long as we are talking about an sbc then you really couldn't go wrong depending on how much power you want to make. Build a typical forged 10:1 with a turbo cam then run a single with low boost and have the same low end torque as any built 350 but twice the power up top. If you can't drive a high hp rig then you can't drive a high hp rig, it's not like this is any different than the high horse motors that don't make any power until 3500 rpm. Adjust your stall speed accordingly.

Right, I understand the difference & realized what he was talking about.

Originally Posted by bbaXJ

If you're at full boost at that low of RPM then by the time you hit the top end you'll have more than maxed out the turbo's, be pumping hot air, causing high IATs and EGTs, risking detonation or at a minimum losing efficiency and power, etc. Sequential turbos would be better suited to technical wheeling, but as has been said already, they'll still make things tricky since in many scenarios they'll either boost when you don't want it or not boost fast enough when you do want it. I was building a GM LQ4 6.0L powered Scrambler that I wanted lots of power in. I originally did a ton of research on turbo kits. Even though I was gonna do lots of dune running and street driving it still made more sense to run a supercharger due to the type/timing of power needed. I still would've been better off spending the money to mod the 6.0L to make crazy power all on its own but I wanted something different. You can make any setup work reasonably well, but the best all-around performance for any type of technical wheeling will be to just modify the engine itself to make as much power throughout the RPM range as possible.....the flatter and earlier the torque curve the smoother it'll be, and generally speaking that'll be easier to do on just motor than on a system that relies on the motor spinning compressor wheels, whether they're belt or exhaust driven.

You think with the proper sized equipment I would have a problem feeding a (pair) 2.6lt engine bank for 3500rpm ?
I'm by no means even knowledgable in this, but it seemed a realistic goal.
You do make some solid points on NA power.

[hammercore]

i personally don't see a real benefit in turboing a rockcrawler for the amount of work it would take. But if you're into sand or mud, hell yeah. Theres a 350 twin turbo mudtruck build in the chevy section iirc.

i was just talking to a friend last weekend who is into drags, his z28 is running a 9.70 in the 1/4 with a bottle. He's planning on getting rid of the NOS cause it cost him about $15 a pass and building a twin turbo engine so the power is always there. From what he told me alot of guys are pulling 6.0 truck engines out, putting twins on them with a good tune and are getting close to 1,000 hp reliably.

[slowlsgt]

You wont see 1000hp out of a bone stock 6.0. Ive seen close to 900hp on a stock one but its not a everyday thing for it. Now you can make 650-700 everyday and the 6l will scream for more.

[JPI Motorsports]

Originally Posted by laproscopic

modern turbo tech is great but...$$$. Properly sizing a single turbo can be tricky- sizing Large motors (v8 small block) are even harder. Now try and do sequential turbo's and pay for all the electronics to make it work. now add dyno time....
would be cheaper to buy a new crate ecoboost

point is that making one off, powerfull turbos work well in a rock crawler isnt going to happen.

I've been pondering this since this thread started.......
After my KOH/Mod build we are going to start on a dedicated Ultra4 car.....
I'm going to have to dig through my turbo pile and see what I have left....
Maybe an IFS twin 72mm turbo'd Ultra4 for 2013? hmmmmmm......

LOL

[89lc]

Why not start with a sequential twin turbo engine. BPU 2jzgte's with the sequential working can make some good power down low.

[73FJBUGGY]

This has gone off base IMO...aren't we just talking about a recreational rockcrawler?! Drag racing and rockcrawling have nothing in common (unless you're coleworx or TC). A good Rockcrawler has low gears and a powerplant that makes enough power to turn the tires...end of story. I have seen a Minitruck with a stock 4 banger and low gears out-crawl a built 350. 1,000hp at 7,000 RPMs isn't useful in a rockcrawler unless you want to line up at the bottom of the hill and rev your engine until your 4,000 stall converter kicks in and launch into orbit (which some like to do...at least it's fun to watch). I'm sure there is a use in Ultra 4, ECORS, KOH, etc racing....but recreational rockcrawling is different. Maybe the OP should qualify what we are specifically talking about.

[Flatty]

I wheel rubicon, fordycew, and the hammers once in a while. I am not competing, nor am I running wide open down a strip. I know there are ways to get the power band to be steady all the way through the RPM range, but generally you feel the turbo kick in around 4000rpm. Witha that said, I like turbos for the lack of altitude sickness. I am constantly going from sea level to 7000ft. less air means less power. I don't know if a turbo setup is necessary though.

Dima

[73FJBUGGY]

Originally Posted by Flatty

I wheel rubicon, fordycew, and the hammers once in a while. I am not competing, nor am I running wide open down a strip. I know there are ways to get the power band to be steady all the way through the RPM range, but generally you feel the turbo kick in around 4000rpm. Witha that said, I like turbos for the lack of altitude sickness. I am constantly going from sea level to 7000ft. less air means less power. I don't know if a turbo setup is necessary though.

Dima

So it seems we are talking about recreational, technical, rockcrawling. So the drag racing and other racing input are not relevant to the original question.
As for your altitude issues, that is one thing I love about propane...there is no change necessary for altitude. I have one Rig on gas and one on propane.

[laproscopic]

now that i put deeper gears in my lexus i dont see the turbo problems as much on the trail. my turbo is actually a bit oversized for my app.

what i like about the turbo is that when i have the truck on the hwy (she's mostly trailer queen now) i can run 80-mph all day if i want. (1500' egt) I have had her to 100mph once with 42's. (at 10psi boost)

[Ry_Trapp0]

boost - turbo espeically - is ALWAYS beneficial now, how well your rig works after a turbo or two is completely dependent on how well thought out your turbo system is. as was mentioned earlier, ideally you would want an electronic boost controller to have control over the boost coming from your turbo. some will allow you to actually set a curve so you can build the boost as slow/smoothly as you would like. of course these controllers aren't cheap, but you gotta pay to play.
all in all, you can make a turbo system operate as smoothly as a supercharger, but it'll require a bit of money and some very careful planning. not quite as plug and play as a supercharger(or NA of course), but at the end of the day you'll end up with the most flexible and efficient engine combination.

as far as sequential turbos go, i would suggest avoiding that sort of set up unless you plan on pushing HUGE PSI(30+). just take a look at diesels where sequentials are most prevalent, guys are running singles all the way up to 60PSI, maybe a little more. obviously they're running massive turbo, but point being that they use sequentials strictly for huge power.

and as far as compression ratio is concerned, there absolutely NO REASON to run low compression. the trend in the drag racing world is increasing the compression ratio because it makes for a more efficient combination. also, the '11 mustang GTs with the new 5.0l are running 11:1 compression, and everyone and their brother has been putting 7-8PSI to them(power increase from 380HP at the wheels to 600HP at the wheels) without a single failure as of yet.
for more info on compression vs boost read this...
http://web.archive.org/web/200801251...ch/forced2.htm

Originally Posted by 73FJBUGGY

So it seems we are talking about recreational, technical, rockcrawling. So the drag racing and other racing input are not relevant to the original question.
As for your altitude issues, that is one thing I love about propane...there is no change necessary for altitude. I have one Rig on gas and one on propane.

drag racing is absolutely relevant, because that's where the latest and greatest turbo technology is coming from. break it down and both situations are about putting power down while maintaining traction. in both cases you want smoother linear power, neither benefits from a surge of power going to the tires uncontrollably. the difference being, the higher end turbo dragsters are trying to put down 3000HP on a 10.5" wide radial tire

[TURNEROFFROAD]

Well I am building a trail/technical - rock bouncing/ hill shooter do all rig. I'm running a variable turbo setup and am going to help it spool with NOS when I want near instant boost and will actually "open" te exhaust housing to keep it from spooling in the technical stuff where I don't want or need the power. Should allow for a tame ( well fairly tame) trail rig and one mean HIGH horsepower quick responding hill climbing rig...


I feel It's a balancing act... Tough to dial in but worth it!!!!