Building on the forced induction post.

I have an R1 block W2 418" small block. It makes about 550-600HP NA and it is 10:1 compression and only runs on the finest E10 91 octane fuel.

For people that know more than me what would a cam change, ring gap change, and a turbo look like for this combo? 850HP on 10lbs? and what Turbo S475? I would probably go E85(actually E70 is available here at the pump) with no intercooler or meth injection just to make it easier to package. In my mind I think if I were to push it harder than that I would want to change pistons to something more fitted for boost, it has some auto tech pistons in it now and boost wasn't in the conversation when they were ordered.

I already have EFI and flex fuel capability. I believe I have enough fuel pump to cover 850-1000HP on E85, if not a 3rd pump isn't hard to add.

I would imagine I would also need to change converters.

No power adders for me yet, but converted to EFI on The Charger and Coronet.
I bought a 2008 6.1L Gen III hemi with Nag 1 trans for $4K (with accessories, harness and stock computer.)
This is for a basket case '69 Coronet I bough that was an ex-bracket race car so it was pretty stripped when I got it, and has already been cut-up a bunch.
I was thinking of having the heads re-built with the Dura-Bond Killer-B valve seats and severe duty valves to handle the heat of turbo charging.

Not even sure when I'll get around to messing with that project. After I got the GEN III engine/trans, a '73 Jensen Interceptor came up for sale at a price I couldn't pass up, so now I have another project car that I can drive while working on it.

Having built and owned many turbo cars, I far prefer twins over single and intercooled over not but that's up to you.

Depending on what cam you have you may not need to change it.

10 pounds will be real close to 1000 hp

Even if the specs were OK for boost(I don't know that they aren't) I wouldn't mind taming the cam down and lean a little more on the turbo to make the power. Its around 275@.050 and .640 at the retainer IIRC, I imagine that could be toned down a bit with forced induction and still make decent power.

I too have a R1 block but have Indy heads and have considered boosting it (turbo). My concern is how much boost will the head gaskets handle with the four bolt design? My block and heads had the extra bosses for the extra row of head bolts on top and bottom. But I had to remove the bosses in the lifter galley to allow the roller lifters to go in. The bottom row is still there.

Yes agree completely, you could run much less.

S475 wouldn't be anywhere close to 1000hp at 10psi. Maybe a pair of 76/75's but that's 2000hp worth of turbo

depends on how much boost you want to run. will it hold 30 PSI? id guess not. Will it hold 10-14 im sure it will with good arp studs, and a quality head gasket.
on one of my imports at 25 psi it lifted the head a little. So now I have to O-ring the head to run 30 PSI. I dont see why that wouldnt be an option for a mopar. they do it all the time on diesels.

My combo is:
Non-intercooled blow through E85.
.040" over 360,
Custom Diamond Racing Turbo Pistons
Eagle H-beams
230@.050 .540" lift hydraulic roller.
9.2:1 compression.
CNC'd Eddy heads.
Stock block with 1/2 fill and girdle. Stock cast 360 crank (never turned).
Cometic's with head studs.

I have ran mine as high as 23psi on a billet wheel S476. I'm guessing it makes somewhere around 900hp at that level. (142mph@3740lbs)

I can't speak to cast crank/stock block longevity with any additional changes. But I think mine would make more power in a few ways.

1) It could use more cam, to turn more RPM. I only shift it at 6200, but more cam to turn 7,000 would be a whole new world.
2) It MIGHT benifit from getting away from the stock exhaust manifolds. They only have a 1 7/8" collector oulet, so could be hurting it.
3) It would probably be quicker with an intercooler of some sort, that would give me more tuning room to turn the boost up further safely.
4) I could put a 4" crank in it, which would allow me to use up more turbo flow (lowering the boost), at the same RPM's, and make more power.


As said... all of the above put the stock block/crank at risk, so I'm happy where it is. (Not to mention it's only got a roll bar in it, no cage.)

Making power is one thing, getting the car down the track is another. Getting the converter right, dialing in the boost/timing ramp coming off the trans brake, and getting the suspension dialed in for the mega torque... are all key.


How much boost and power the parts will hold is COMPLETELY dependent on the tune. I have found that more boost/less timing is WAY safer, than less boost/more timing.

^ I don't think more cam would help you. Have you tested turbine drive pressure? I think with a single that size you would find it's getting up there and that's what's making it peak early.

You could keep your current cam and go to twins, reduce turbine drive pressure at the same boost level and pick up a ton of power and 1000 usable rpm.

More cubes would make less power with your current setup. (again because of drive pressure to boost)

The manifolds would have to be horrible to pick up anything with headers so not much gain for time invested if what you have fits well.

Agreed that an intercooler would gain power.

i am running a air to water intercooler. I have a small fan on the heat exchanger and it works very well.
on a 106* day on the dyno at 24 psi my intake temps were only 114* not bad for a ton of ambient heat. I am thinking of one for my next turbo project, small water box in the trunk with a Bosch pump and a decent heat exchanger anywhere with a cooling fan on it.

i will probably try one of those tube style versions for my Mopar.

Its basically a 76mm Compressor, but with an 88mm (or 96mm inducer depending on how you want to measure.) Turbine setup with a T6 flange and a 1.32 A/R. Very unlikely a 360" motor at 6,000 RPM is even close to choking on that.

There are guys pairing the billet 80mm wheels with this turbine making over 1200hp on LS motors, so I don't think I'm really at the turbine limit.

What COULD be possible, is that the single 1 7/8" manifold outlet is the choke point. Hard to say without trying other stuff. But as you mentioned, that is a lot of work to build a set of headers just to "what if".

I have no interest in pushing this combo any further. It's plenty fast for a street car with only a roll bar, and is reliable enough to bracket race.

I thought a lot of things were very unlikely myself. And then I tested them.

Each manifold has a 1 7/8 outlet? Well you could test drive pressure at the manifold before the outlet and then right before the turbine. If there's higher pressure pre-outlet it could be a restriction but I doubt it.

T6 twin scroll narrows down to smaller than that not too far past the inlet flange.

Anyway as far as cam specs and RPM, I ran a 236/236 112.5lsa hydraulic roller cam in a twin turbo 427 LS7 and it peaked at 6900, barely dropped off by 7800 and made 1,341 to the wheels at 23psi boost.

Twin T3 PT67/66

Just saying that you don't need a ton of cam to make high rpm power with a turbo engine. If yours is falling off at 6200 I would start testing things as I don't think a cam swap will help you. JMO

S480 was the turbo size I meant to post, but I haven't done an ounce of research on that.

JustinP my R1 block has had all the extra holes milled off. I currently run a Cometic gasket but only because of a deck height miscommunication and they are the only one that offers what I need. I imagine even if I changed pistons I would run cometics if I added boost.

I currently run a Pro Dominator tunnel ram converted for EFI. Would there be a benefit with keeping the tunnel ram but having a custom top made for it and run a single throttle body, Or put an elbow on my single four manifold and go that route. Either way I think it might let me go with a stock hood and I really want that back.

I'm not familiar with the AutoTec pistons? Would be worth a call to them to ask how thick the crown is, and how far down the top ring is. Could work... just need to investigate.

I would look at it this way.

Use what you have, and get to the potential of your parts in hand. That might mean the pistons or 10:1 compression ratio w/iron heads limits you to less boost. But it would still make good power none the less...

or

Sell the motor and start over with a Gen 3 hemi.


I would NOT swap the cam (for ideal specs), swap the heads (to aluminum), build headers, swap the pistons (stronger/comp. ratio), etc... just to get back down to your usable crank and block.

Its basically a 76mm Compressor, but with an 88mm (or 96mm inducer depending on how you want to measure.) Turbine setup with a T6 flange and a 1.32 A/R. Very unlikely a 360" motor at 6,000 RPM is even close to choking on that.

Higher airflow will artificially choke that turbo. I guarantee you that if you log your exhaust pressure now, with the current engine, and later put a bigger compressor wheel in it, you would see a drop in exhaust pressure, and more power.

I'll guess 53psi turbine drive with 23psi at the intake

I can't wrap my head around this one, could you explain more?

A bigger compressor wheel moves more air at the same rpm. Since boost is controlled by air instead of turbine speed he would not need as much exhaust flow to hit the necessary turbine rpm. Once the speed required is reached the wastegate dumps the rest overboard.

*poof*

Same intake pressure but with less parasitic loss in turbine pressure. That means more power.

The larger wheel will likely be in a happier part of the compressor map than the current wheel. Improved efficiency also means more power through lower boost temperature.


Think of it as paddling a canoe with a ping pong paddle. It'll work but you're going to spend a lot of effort getting up to speed. Changing over to a proper paddle means more speed with considerably less effort.

Think about what is going on. How does a turbo work? The compressor section is a centrifuge. The bigger the wheel diameter, the lower the rpm the centrifuge needs to spin to move the same amount of air. (Lower cent. force per diameter with higher air flow.) If you agree with this, then you need to do two things to make sense of what I said. You have accept that BOTH wheels are spinning slower with the same intake airflow, and... you have to accept that centrifugal forces do not cease to exist in the turbine side of the turbo. Higher turbine speed will have a negative effect on flow through the exhaust side of the turbo, regardless of a/r, because the gasses are fighting the centrifuge they have to move through to exit. The profile of the turbine wheels are designed to minimize the effect, but you can’t eliminate the fact that you are essentially using the engine to force its “waste” through a centrifuge in a direction that fights the natural tendencies. Slowing down the wheels helps with the fight.

Yes but this is all a balancing act. On the other end of the spectrum there are many turbos out there with too large of a compressor vs turbine (like 76/66) and that will result in the same problem, excessively high drive pressure.

That's why I think twins are better every time. For a given potential airflow you end up with faster response and less drive pressure compared to a single.

Agree about the balancing act, but the turbo you mention is hard to beat on a 5000 rpm v6. All caters to many variables. Testing testing testing.

IMO it's just a mismatched unit. I would rather the compressor and turbine be capable of similar power levels. So if I have 750hp worth of turbine give me a 66mm compressor instead of less response from a 76mm capable of 1000.

I would stick with a turbo that has compressor maps available, BW or Garrett. Your unlikely to find someone running a combo that will be similar, so trying to find a proven combination is not going to be GM LS easy.

Both BW and Garrett have programs, Match Bot , and they are very good. Make sure your data entered is accurate, and pay attention to where you are using the turbo in it's compressor map. I like the MatchBot because I can make changes to the formula to best make use of a combination.

I am running twin EFR 9180 turbo's with Tial 1.02 housings. Using MatchBot, this was the best compromise for staying in the efficient part of the compressor, spool time, and EMAP (back pressure in the manifold).

Makes sense @feets @TRENDZ

For those of us who are hobbyists vs hard core, you shouldn't discount the amount of fabbing and cutting. Twin T4's might be the best theoretically but be terribly difficult to package in a car that needs to maintain it's OEM inner fender wells and such for other reasons. A single might be easier to package for most cars with power brakes and power steering. A T6 is a BIG thing to fit as is a 5" downpipe. A single T4 turbo can be the easiest item to package and be successful for a hobbyist. Matching your cubic inches to a turbo size that you can package, e.g. feets' original beast may have been better served with a 383/400 making the same or better power more comfortably/economically.

I have a 383 in my Fury for a reason vs a 440 or stroker. I'm using a 5.7 in my Coronet for a reason - allowing me to more easily package appropriately sized turbos and still have the capability to make more power than I'll use/install safety equipment for.

For those reading who aren't intimately family with turbos...
Turbos are not free power.

In this world you don't get something for nothing. The same goes with boost.
Any real street car with a turbo will have more pressure in the exhaust than in the turbo. Compressing air takes work.

Oh, but it's exhaust gas you say. Your breath is exhaust gas. Ever notice you have to put a little effort into blowing up a balloon? Try blowing up a car tire to 20 psi. Think you'll get there by puffing on a valve stem?

The engine is experiencing the same issue. It has to work to build up that pressure. However, instead if a fixed container, it has to maintain that level of work until you get off the throttle.

Turbo lag? That means the engine hasn't worked hard enough to get the turbo up to speed.

Turbos can be very efficient but they aren't free.

I have not measured it, but I do have some information.

I only run a 2psi wastegate spring, and rely on the boost controller (on board air tank) pressure into the top side of the gate to make the boost. Basically it requires 1psi of gate pressure, to make 1psi of boost. If the backpressure was at 53psi, it would be blowing that 2psi gate spring open for sure. Also, the car does not like RPM regardless of boost pressure. Even at 10 or 15psi it doesn't like RPM (ET slows down if you shift it higher).

But in principal, I do agree any combo can benefit from lower backpressure. 100% agree with that. But it's not the end all, be all, of a combo.


I would think a S480 combo (80/88) at 850hp goal is a great choice for the original poster. 80mm compressor will make 850 easily, It will spool relatively quick, and the China Knock off versions can be had for $750 or so in billet wheel form. I can't see doubling the complexity and cost with Twins being worth it in a build like that.

Easy way to find out is to measure it. Probably 10 minutes worth of work if you are interested in finding out.

Twins aren't double the cost or complexity. Just depends on your goals.

Yes you can make almost any power goal with a single turbo. If at the same power level you want much faster response and the ability to hit peak boost/torque at a lower rpm on a street car, twins will make that happen.

[u][/u]I've driven Dizusters car on the street. It's hard to manage the "response" now. It doesnt need anymore. A 5 second burst gets you to where you dont need to be on the street. Racecar is a different story. We can always go faster.
Doug

Yes all preference. I feel single turbos are harder to manage as you can go wide open throttle and get a big thump of boost as it hits.

Twins can almost follow the accelerator pedal as far as response so easy to roll into it and maintain traction.

That and more so, just response during part throttle driving.

Agree. Changed over a customer car to twins from a single. Much more predictable and followed the throttle better. A bigger single gives that “2 stroke” feel of a power rush.

For sure, great analogy.