Katech_Jason

iTrader: (19)

Haha, no we're not. It would be very interesting though.

Old SStroker

Limiting average piston speeds (PS) haven't increased all that much in the last 10-20 years. Mostly the strokes have been shortened to get the rpm. When F1 engines had 80mm x 57 mm engines, they were spinning about 14K with approximately the same PS as today (~4900 ft/min). 4.5 x 3.9 ProStocks were more like 8000-8500 rpm than today's 10K 4.9 x 3.3 engines, but with still about the same piston speed. Today's ProStock has an average PS over 5500 ft/min, which is borderline "insane" and close to the highest you'll find.

If the 2.4L V8 F1 engies get to 21000 (with max 98 mm bore limit) they will be just about to 5500 ft/min that the ProStock sees.

FWIW, the 4.125 x 4.000 LS7 has a PS of 4667 ft/min. @ 7000 rev limit and the current 2.2L Honda S2000 has a PS @8200 redline of 4879 ft/min.

MrDude_1

iTrader: (4)

if someone could comeup with a seal that let you run large hp thru one (boost) and have it last as long as a normal set of piston rings, there are 1000s of us that would jump to rotarys...

but ever since day one, thats been the large problem with the rotary... that damn apex seal.... that and emissions pretty much killed the chances of any other OEMs picking up on rotary technology... it would be a insane amount of R&D (and money) for a OEM to build a rotary from scratch to meet all of today's standards and expectations...

DavidNJ

For an Ultima, a 325cid 8000 rpm engine makes sense because of the transaxle torque limitations (unless you're spending $20k on the transaxle).

Then, my all means. I would also use Ti rods. After spec'ing your head, probably a custom from ET (give them a call), You'll be using big valve springs, Jesel rockers, solid roller lifters, and Ti valves.

you can have Crower (or Callies) put together a custom setup. Crower can give you a dihydral light crank in the small stroke. Callies has an equivalent. Crower will make their own rod. Callies will ship from Carrillo. In this short stroke setup you can use 1.88 or 1.78 rod journals. In either case a custom CP or J&E piston to match the block and head.

Oh, the block. Either a C5R, LS7, or World Castings. In all cases you'll have either a 4.125 or 4.155 bore. The crank will have a 3.25 or 3.335 stroke. For street use the LS7 dry sump is ok, and they can make the crank to drive it. Otherwise there ARE, Harrop, and some other Aussies have dry sump pans with pumps. ARE also has valve covers with spring oilers, which should increase spring life if you decide to use a cam with an aggressive ramp (preferred IMHO).

You have a lot of options on the cam. I would go for a fairly mild duration with quick ramp and lots of lift. This would keep the idle reasonable. Whatever lets it peak at 7500-7800.

For the intake you will use the Harrop ITB. Or a custom ITB.

For electronics you can you a Chevy setup, or a Autronic, Motec, or equivalent. With the aftermarket units you would be able to drive peak and hold injectors, allowing more control for idle. You would also be able to use a CDI with CDI coils.

For an Ultima (or a FFR GTM), the Motec or equivalent ECU would drive a digital dash display. They also incorporate traction control using wheel sensors and if you spring for a sequential transaxle, they can drive that with clutchless shifts (a strain gage input tells it when to match the revs).

This should be backed up with a double or triple disc carbon clutch with aluminum flywheel.

Details will include an ATI damper, and possibly an electic water pump (BMW uses one on the new M5, and with the Motec or equivlant you may be able to drive it to maintain a specific coolant temp.

Ferrari uses a flat plane crank, and that may be possible here. However I don't know the LS1 issues.

Any case, my idea of an Ultima/GTM engine.

SStrokerAce

iTrader: (2)

Forced induction has nothing to do with letting the motor run to more RPM...

Considering that the Supra is a OHC motor without pushrods, it has small valves in a 4 valve head and a block that was basically designed by Chevy half a century ago....

If anything the forced induction ADDS problems to turning the RPM.

As for a head that will work with RPM on a 427 LS1 that's not the hardest part it's the PISTON SPEED with a 4" stroke like OldSStroker said.

Bret

DavidNJ

Yes, the Supra has a great top end. Built to rev. However the issue was the bottom end. But your right, the 4" stroke is a killer. If he used a 4.2 bore, he could get away withy 3.85 stroke. Using a World block with 9.8 deck, you could use a BBC sized 6.65 rod. Almost there.

But back to FI. It doesn't help with crank speed. But it does force more air in the engine, allowing it to breath without a head that otherwise may be needed.

However...427...8000rpm...650hp...??? The displacement, engine speed, hp, and application are out of wack.

SStrokerAce

iTrader: (2)

That World block is going to be vapor ware for a long time IMHO.

speedracerz

iTrader: (8)

I am in the works of biulding a high rpm ls6. to start i went with a 3.779 stroke crank, this stroke gives the ideal 1.6:1 rod/stroke ratio. a good balance and blueprint goes a long way. forged everything. as far as valvetrain. solid camshaft and shaft mounted rockers will go a long way too.

SStrokerAce

iTrader: (2)

There is no ideal rod to stroke ratio BTW

DavidNJ

Do you really think so? I thought they were pretty good at getting stuff out the door. The big problem to seems to be the $5k list and probably $4+k street price, IMHO

speedracerz

iTrader: (8)

this has been debated for some time now.......rod / stroke ratio varies where your power band is going to be. old school here you stroke a 350 to a 383 it is going to make more bottom end torque. take the same 350 and destroke it to a 327 and you will get a higher power band and more top end hp.

a 1.6 is the lower limit for an aceptable rod ratio. any lower (bigger stroke) and you push the limits of rod angles and create more stress on the crank which would be multiplied at higher rpm. so a 1.6 ratio is ideal for a higher rpm setup.
it would actually be a 3.828" stroke crank would be the largest stroke you would want to run for a high rpm setup. my 3.779" is actually a 1.62:1 which will move the power band a lil higer. both numbers are figured using a 6.125" rod

DavidNJ

Stroking an engine without changing the cam/heads/intake/exhaust changes the powerband because it change the VE/rpm map.

Yes, a different stroke/length ratio may work differently with different cam/intake tuning. But from a force standpoint it is not rpm sensitive. Tradeoffs include increase weight and reduced stiffnesws from the longer rod, so there are some physical limits. However, without those tradeoff (VE tuning and mass/stiffness) longer is always better.

SStrokerAce

iTrader: (2)

No, there is no ideal rod/stroke ratio period... if thats the only variable in the system. There might be an ideal rod length for a certain setup, but rod ratio is BS.

If you need help with your thoughts on this... http://speedtalk.com/forum/viewtopic.php?t=2177

Bret

MadBill

That's for sure. With the right parts, a 427 LSx can make way over 700 HP @ 6,000 RPM, N/A.

Louie83

iTrader: (3)

Good thread, I've learned a lot already. So basically the pistons in a big cubed motor, when making 7000 rpm's, are moving at much greater velocity than a tiny motor making 7000 rpm's (obviously).

Is this more or less the reason why little Honda OHC motors redline at such high RPM's and have such a high peak hp for their size? And why tiny crotch rocket engines have even higher redlines and even great peak hp for their size?

Therefore, ricers who talk about hp/liter are even more retarded than I previously thought?

racer7088

hahahahahahaha! Our 4 inch stroker LS1 turns over 9000 rpm! Goes 155 MPH in the 1/4 at 3280 or so and is turning way to much piston speed. I guess the LS1s with ported LS6s heads just didn't know they were exceeding the "piston speed limit" set forth by others? Actually peaking at like 7700-7800 ish the orange cars engine makes peak power at 5200 ish piston speed!

It is true that most heads won't go way over 5000 though. After that they are on the way down in the powerband.

Old SStroker

Congrats on getting it to live @ 9000 (and 6000ft/min). That's a ton of load on the rods, or many tons.

Did you say the 9K engine makes max power at 77-7800 (5200 ft/min)? Do you shift it at 9000? That seems like a lot past power peak.

GTOTitoLS1

racer7088, My Dad and I been building chevy engines for the past 17 years, my dad alone for the past 40 years, since chevy first introduced small block 5.7,350 engines.
It all comes down to LS1 it just a old mod to date 350 block, same thing you will find in a 40 year old 350 small block you will find in a LS1 except LS1 all aluminum. WE have a 4 bolt main 350 with a 383. stroker kit, and edelbrock heads with 564 cam we hit 10,100 rpm on the track, Dyno showed after 5600rpm slight loss in hp but we knew something wasn't right because we weren't getting half of the hp. we installed titanium retainers , cranck and push rods and rockers. tested again o and the engine output at rpm varies on cam we had a cam that could hold 11,000rpm, after 5600rpm hp droped again but we kept going higher at 6500 it started to gain again at 7000 reach 1000 hp then at 9900 it reached 1350hp and at 10210rpm it drops again, so I know for a fact you could get a Ls1 to go 9000 rpm without droping HP, but you have to work the whole internal engine.

GTOTitoLS1

Also I made a 2004 GTO Ls1 go 8200 without loosing HP, it's twin turbo though

MrDude_1

iTrader: (4)

before i make a large post pointing out all of the improvements and differences in the shortblock, could you re-clarify that?