Turbo's for the street
 

Are 100mm turbos to big for the street,I'm kicking around a TT 499 sbc

twin 100mm turbos? :eek: what HP are you looking for, 4000 or so? :wow:

Jody

not to hijack... but the question has been haunting me... what size turbos to mount on an ls1, and i dont want 1400Hp, but somthing realistic... 650 rwHp?? or that teritory.. we have 95 octane available here, and the engine is an ls1, 8:1 comp, good heads.. dart? and a good intake.. air/air intercooler..

is it worth going ball bearing, they are more expensive and do not come with a warranty...

Well that's the reason I asked,I'm a nitrous guy so this whole turbo deal is a new world to me.

I would like to be in the 1300ish bracket.

THE 100MM'S TURBO'S OVERKILL , A PAIR OF 70'S WOULD BE MORE THAN ENOUGH. AND A NEARLY 500" SB WOULD BE A TIME BOMB. THE CYL. WALLS WOULD BE QUITE THIN , AND THE STROKE REQUIRED WOULD MAKE FOR A WEAK CRANKSHAFT. NOT TO MENTION THE PIN LOCATION WOULD COMPROMISE THE RINGSTACK MAKING THE PISTONS NOT VERY DURABLE. I THINK THE SAFE LIMIT FOR MOST TURBO SMALL BLOCKS IS A 427CI. IT'S A 4"STROKE WITH A 4.125 BORE THIS LEAVES THE BORE STABLE,AND LEAVES ROOM FOR A COUPLE OVERBORES IF YOU HURT IT. BUT IT STILL NEEDS A TALL BECK BLOCK FOR BEST RESULTS. IF YOU WANTED TO STAY WITH A SHORT DECK I'D GO WITH A 3.750 STROKE. CHECK OUT NELSON RACING ENGINES AND YOU'LL SEE WHAT A MOTOR LIKE THIS IS CAPABLE OF.

I didn't mean to be a smart aleck, but a 100mm turbo is HUGE, supporting about 2000 HP depending on model. That's for ONE turbo; two is insane for anything on the street and the spool time could be measured in minutes. Kidding on the spool time, but you get the idea.

What is your HP goal? As far as small blocks and turbos, most of the real high powered setups are under 400 inches.

Jody

I just finished acouple 499 dirt late model engine's,tall donovan blocks.both made 1100hp and a friend of has a pro street vette with a 648 and want's to change to TT's and use a 499 for base.

I noticed most go smaller cube's,me and freind of thought it would be cool to play with a bigger inch motor and TT's has in my other post it's replacing BBC.

But I was looking at what alot of the 10.5 racer run for turbo's and just kinda through a # out to see what response I got.

In my experience there are trade-offs in forced induction builds depending on cubic inches. My 468 made a bit more HP than my 540 with the Procharger at the same boost. The 540 beat it in torque though. Seems like there is so much weight in a big inch stroker that maybe the smaller setups are more ideal, at least as far as HP is concerned.

It just seems all the fastest small block turbo guys seem to be in the 370-380 cid range. And they don't have a cubic inch limit, or budget concerns. Seems if a 450-500 inch small block would make more power and a lower et they'd use it.

Jody

Don't forget that dental-floss thin headgaskets between the bores on big bore SB's can cause you quite a few headaches when you throw a lot of boost at it.

Go big enough on the bores to unshroud the valves, but not so big the sealing ability of the headgasket is compromised. On a SBC with standard bore spacing I don't think I'd go over a 4.125" bore... but that's just my opinion.

As was already mentioned, going too big on the stroke poses other problems like piston speed and a compromised ring pack.

I also agree that somewhere in the 370-390ci range is the "sweet spot." I'm planning on building a 388 using a 4.125" bore Dart block with a 3.625 stroke crank sooner or later, unless I decide to make the jump to LSX.

A set of PT-67'S are GREAT turbos and will make 1300 hp like nothing. You will wish you went turbo many yeasr ago after having them. I cannot describe how great it is to make such huge power all day every day. The car will drive like stock, but make insane power at the push of the pedal. No need to fill a bottle, throw belts, or loud whinning.
Part of the reason to go with smaller cubes is efficiency and need. A Turbo can make up for cubes with boost up to your octane limits, after that, it is time to increase cubes. A typical 330-400" turbo motor will make an easy 1200-1500 hp under 30 psi on 116 octane. Do you need mre then that?? If you want to build the ultimate pumpgas engine, a turbo 800" mountain motor will make an easy 1800+ hp on 93 octane pumpgas.
The downside to massive cubes on the street on a turbo car is the efficiency. If 80% of the driving is done at part throttle, a 350" motor will suck about half the fuel of a 540" motor. So for a mostly street driven car, I would go small cubes for efficiency and weight, and cost savings.
If I wanted to race and had a chassis car, I would build the biggest motor possible and slap a turbo on it!

Well a smaller motor would run less fuel,but this isn't a DD so we aren't really worried about mpg.

Pt-67's what mm are those,This going to show my knowledge on turbo's,I know turbo's work on gas pressure etc,so how do you set the psi on one.Like I said this a new beast.

My brother been running a 10.5 car with a nitrous 555,and has been talking about a but turbos on a 706,I told him I wasn't ready to play with that kinda monster yet.Plus the chassis work needed to make a turbo car leave.I have raced acouple turbo PM's and they are a IMO more bitch to may leave than nitrous car.

Thanks for all the advice,help guys

A PT-67 is a 67 mm turbo. Boost is controlled electronically through a set of wastegates on a twin setup. The wastegate is a valve that either stops or allows exhaust gas to bypass the turbo. If the valve is open all the way, very little exhaust from the engine goes through the turbo, it spins slower, and you get little boost. If you close the valve all the way, all gasses will go through the exhaust turbine and turn it as fast as possible. If you did not run a wastegatem, boost would probably climb upward of 50 psi depending on the setup. This would be bad.

and remember that a PT67 will support almost 800 HP, so two will support 1500-1600. Obviously dependant on the engine combo and boost level.


So again, what is your desired HP goal? You don't want too large of turbos either, as they'll just be soggy, boost will lag, etc.

Jody

Good point.

You should specify what you want the car to do.

-Motor size
-Car weight
-Exact intended use
-Realistic power that the motor will really see

These are the most important things, this will at least get this in the correct direction.

the car this 499 idea is going is a pro street corvette,cruise night,car show cruiser,not raced,I'm not sure why they built a 648 for it anyway,but what the hell.

Basiclly my buddy like's the idea of TT's and wants the around the same hp has the bb.which it's in the 1000hp bracket on the motor.this part i have taken in to thought,it was what turbo's to use and etc.that I was in question on.

the wastegate/blow off valve must be what cause's the burst of sparks or flames under turbo cars at mid to full throttle.

the car a 5 spd lenco in it for a tranny.so it wont break.

this is one of those over hp car's,and the guy has more money and not enough stuff to spend it on.

Step back and re-think what's the goal here.

~1000hp with reasonable manners and durability for a Pro-Streeter.

That being said, a 499" combination may or may not work well. The key is to build the combination for power and reliability. Having thick/strong bores, proper pin height for a strong piston and well placed ring package, good rod/stroke length to control piston speed and side loading etc all factor in.

Next...having a set of proper heads that will be efficient with the engine size under them.

That being said, I would consider a 427 or 434" SBC using a tall deck block, a well prepped set of 18* heads would easily do the trick. Consider a pair of PT70-76mm compressors with S trim wheels and a good intercooler. This is a solid foundation w/ plenty of room to make additional power.

He does not need all that for only 1000 hp, that would be way overkill.

Does'nt really sound like he even knows what he want for sure anyway.

I agree but.....

Would you recommend a pair of TO4E's and 23* heads on what he's after? I wouldn't. That's why I stated the obvious and explained how much room there was to grow with that setup.

It can be done w/ a simple 355 combo.

I'm doing a TT572 Hemi w/ twin 88's for a customer that never has the intentions to use all it's capable of. Is it efficient for what he's doing right now? No but, it's kinda the same deal...he wants the "bling" and has the money to pay for it.

No I don't, I have been try to get him to decide what he wants to do,the engine's not a problem to build for me I pretty well have it figured out,build it with the same crank,rods,pistons I would for a nitrous motor.then change the cam and compression ratio.

I was thinkin about using the same heads I did on the other engine's,15* heads then use a sheetmetal intake.

But right now I'm resreaching this out.

Does he not have a power goal? Mostly street, track, ? 1/4 mile or road course?

Jody

What works for nitrous and superchargers is not especially friendly with turbo combinations. Ring location, pin height, stroke and rod length. Turbos are "closed loop" power adders that are abit more sensitive to intake and exhaust design, head flow/efficiency vs cubic inches etc.

I prefer a single plane intake vs the sheetmetal deal. We've seen better air distribution using a common plenum/elbow setup. See pic
http://img.photobucket.com/albums/v2...s/MVC-002S.jpg

Depending on how the design ends up, the cam can be very mild to moderate as compared to a blower/nitrous cam. Once you get a better idea of what he wants....feel free to post up some ideas and we'll be glad to help.

He want's the same power level has the 648 thats in it(1000hp),which honestly is overkill,it's around town,cruise night queen,trailered everywhere else.honestly the only time it's been run hard is the couple times I have driven it,he's one of the just because it looks cool kinda guys.

With what I have gathered here and some other site's I think 70mm would fit just fine,and if I get the go ahead,I'll throw some combo's together and see what you guys think.

Well I thought for sure a turbo would be like a nitrous set-up and love air flow.I wouldn't have guess'd a single plane style intake,would work best,I'm sure it's subject to application too.

they definitely benefit from good heads, but the intake is not as critical as a nitrous setup as the air going through the intake is under pressure, not drawn through like a n/a or nitrous setup.

Jody

Well he thold me he wants to switch it to a turbo set up,but wants a bbc,so I've been throwing around acouple set-ups,either a 468 or 509.idea's welcome

it sounds like you need to sell him on a particular idea and stick to it.. and weather the displaement is 496 or 509 really wont matter, the 496 might be a little more street friendly and will rev slightly less agressively.. and thus be a little less hazardous to drive but thats only marginally.. i think you need to move on to asking hom decitions he can actually make.. does he want the intake polished or satin... and so on... and tell him that you will make the engine fit his needs and ask him to tell you what they are...

i think ka67_72 did a set of equal length BBC turbo headers in stainless.. send him a PM and see if he cant whip you up a set.. looked awesome, the primaries were alittle to large diameter if you asked me.. but it sure looked bling!

http://hotrodders.com/gallery/showph...cat/500/page/1

http://hotrodders.com/gallery/showga...00/ppuser/7803

Well that's my plan I tried to sell him on a sbc deal,but he thinks since the car has a bbc it will be easier,but he doesn't understand the whole engine compartment will have to redone,I've been playing with a combo to sell him,I just don't have all the details worked out yet.

well, what if you had a lunchbreak meeting where you with some visual aids.. mockups of turbos, aluminum flex-heater hose, pictures and carefull explaining made him understand that a big block would empose some bad-compromise inducing space constraints.. you might even use a tape measure to get the point through... and sell hom on what ever you think is the right package... i mean you are the pro..

but a twin turbo big block.. it sure sounds cool when you say it out loud :thumbsup:

Well kinda the way it went when I tried to explain everything,I'm just going to build the motor.He's talking to acouple guys on the actual turbo set up.the crap we go through for friends is unbelievable sometimes.

I have a single 97mm turbo on a 350 in a jaguar. My 53mm single turbo 302 ranger is more fun. Kids are putting these monsters on Hondas and saying they can spool. I wanted to see what too big off a turbo was like so I did it. I haven't got the car where I can really lay into it yet but I don't think it's going to do anything. Looks huge, makes noise and thats about it. I've got it to make a few pounds of boost but it's time to shift by then. I'm going to find something smaller. The TT454 headers are almost done with 105 hours into them. I'll gladly build a set for anyone who wants them. I don't know what kind of power they'll make but they sure draw a crowd.

http://hotrodders.com/gallery/showga...00&ppuser=7803

Thanks,
Kevin

I think I have him talked into a 454 sbc TT set-up using a pair of 70mm.I have to research cylinder heads some more,but I think 18* degree's will work fine.

Any thoughts or opinions,I'm open to suggestions.

I am not so sure a 454 sbc combo would be so stout with a turbo setup. The Super long stroke added with the crazy torque a turbo makes will make havok on your rod bearings. Just a thought.

Also, take my tiny little $5000 basic 347" LS1 for example. It makes 1000 hp on 93 octane pump, will he need a 454??

rocketman....I have a twin turbo smallblock, a 10-71 blown intercooled big block, have had other turbo and blown cars and if I were starting with a clean sheet for a customer I would go with a twin turbo LS engine. They are great engines that hold up to lots of hp and don't leak oil etc. The LS engines are where all hipo development is headed. Talk your customer into it and find a way to make it look killer. He will love driving it and he won't be bugging you because it breaks or leaks oil. Two cents from a guy that has been there-done that again and again and again.

Amen brother.

http://www.camcojb.com/malitude%20078.jpg

Thanks for the idea,to be honest I didn't think about LSX stuff.

Ok so let's take that 500+ CID motor and the 1000hp goal.
Can I use twin 67mm's? I've heard they can make 1000hp?"

Nope! There's nothing wrong with twin 67mm's they will definitely make 900hp, just not in this scenario. Here's why: 900hp represents a fairly constant amount of air/fuel mixture, regardless of whether it's being made by a small motor at high boost (eg. 380ci at 20psi) or a large motor at low boost (eg. 500ci at 10psi).

The first problem is that most turbo compressors are only able to reach their maximum airflow when they are running at high boost levels. For example, a GT42 is able to flow about 94lbs/min of air at 32psi of boost, but it can only flow around 64lbs/min of air at 10psi. Often people are quick to assume that high boost means high heat and therefore decreased efficiency, but in reality, it takes higher boost levels to put most turbos into their "sweet spot". In this particular example, the turbo is capable of almost 50% more HP at high boost levels than it is at low boost levels.

The other problem is related to backpressure. If the exhaust system (headers, turbine, downpipe, etc.) is the same between both motors, the backpressure will be roughly the same. Let's say the backpressure measures at 48psi between the motor and turbo's exhaust turbine. The big motor will run into a bottleneck because there is 48psi in the exhaust and only 10psi in the intake (a 4.8:1 ratio). This keeps the cylinder from scavenging/filling fully and therefore limits power. The small motor, on the other hand, has 20psi of boost (only a 2.4:1 ratio) to push against the backpressure. Therefore it is able to be much more efficient under these conditions.

The bottom line is, as your motor size increases, your boost level will go down (in order to achieve the same power level). In such a case you will need to maximize the flow potential of your compressor and minimize the restriction of your exhaust system (including the turbine) in order to reach your power goals.

So in summary you need to have a turbo compressor that is efficent at a lower boost like 10psi. In a perfect world on a 500cid a big single like a 101mm would be ideal.

Thanks,

So in a nutshell if you are going to use big cube's might as well make big hp,rather than choke it down.i have been playing with some #'s and a single big turbo on a large cube motor could easily make 2k hp.

No, what he is saying is that you will only need lets say 5 lbs of boost to make 1000 hp on a 540 versus about 18-20 lbs on a 350.

Real basic...Hp requires air/fuel. A turbo is rated by the amount of air it flows. A pair of tine 60-1 hi-fi's will make 1100 hp on a 347" at 21 psi, and 1100 on a 454" at 17 psi. So regardless of boost, they are only capabale of flowing a certain amount of air regardless of motor size. Just need to make sure they have properly matched Exhaust housing to keep the turbine speed in the sweet spot.

To me is does not make sense to do a high dollar big inch motor to only make 1000 hp.

An ls1 is the best engine ever made. Look at my factory headed tiny 347"!!

Well after I sat and reread it I follow that,4 hrs sleep this morning,is making it alittle hard function,anyway this project is spiraling out control at a fast rate.I just had lunch with guy and he's coming up with this monster turbo idea,I told him I can build it,I need a plan and stick too it.