hybrid motor idea-criticism

[Cdc1221]

So heres my idea. 2.0 block, possibly bored .5mm if needed, standard 4g63 forged pistons matched to the bore, a 4g61 crank, and longer rods to make up for the shorter stroke, all resulting in an oversquare 1.9l capable (hopefully) of 12-13k rpms. Anybody see anything wrong with this? I want to build it

 

[LandSpeed-DSM]

The valvetrain, clutch and transmission to go with are whats wrong with it. This would have to be a dry sump motor as well. This would require some serious rod-bolts and a piston strong enough to not have the pin ripped out of it.

You'd be rolling in bearings often at 13k. Not to mention pinning them, as this would likely need an aluminum rod for the weight savings.

Also.. you will need a very large turbo in a very large turbine housing to take advantage of that and make it worthwhile. In the neighborhood of an S400sx-80 is where I would start.

If you have the funds go for it.

I only plan on spinning to the mid tens if I absolutely have to, and the requirements for that are pretty steep.

 

[Cdc1221]

Nice insight. I was already figuring on new trans gears to take advantage of the higher rev limit, and a twindisk setup for lower momentum. I was thinking of valvetrain. I wonder if new guides could be set in a dohc head to use the smaller-shaft 3g 4g64 valves, to lighten the valvetrain. Ive just always loved a small displacement, high rev engine.

And no im not made of money . Maybe its something ill play with later down the road.

 

[LandSpeed-DSM]

You'd be looking at an easy 17-20 grand, even doing everything your self.

 

[Cdc1221]

Ouch. What i get for thinking outside the box. Just trying to do something different to my 2g that noone has before.
..

 

[LandSpeed-DSM]

Well.. using a shorter throw crank in a larger block isn't exactly novel.

The 2.1 is the same concept, and how many of those do you see around? I can think of 2.

I'm not sure they are being used as intended either because of the prohibitive cost of supporting mods.

A dry sump alone is 5.5k.. something as simple as finding valve springs that can handle 13k with the ramp rates and net lift needed, while having the pressure of boost on the intake and drive pressure on the exhaust fighting them as well becomes a real headache.

You have to have them shimmed enough to stay on the seat, stick to the nose of them and make sure they are at an installed height that clears the pistons and doesn't bind.

Formula 1 cars that wind through 13k use pneumatic springs.. some bikes use desmodromic valvetrain.. unless you have a need to do it, it's not worthwhile to just have an rpm goal.

The only reason I am considering going that high is because I am looking to eventually do 225+ and I am gear/tire limited. If I can get away with it, I'd rather stick to high 4 figure engine speed.

There are other examples of why you would wind that high.. trying to light a very large turbo, looking to make more power while keeping torque below a certain threshold. That sort of thing.

But just being able to say "my 2G revs to 13k" is somewhat silly, in my opinion at least.

 

[Cdc1221]

Hmmm. While i knew it wouldnt be a walk in the park, i couldnt help but think of the simplicity of a sportbike engine when this idea came to light.

If you wouldnt mind, could you tell me the purpose of the dry sump setup?

 

[LandSpeed-DSM]

Spinning our stock Oil Pumps that high (intended for a max of ~8k rpm) and the difficulties that come with trying to drain the head of all that oil so the pan doesnt empty out. Among other things.

A Kiggly HLA helps considerably, because instead of dumping that oil into the head, it restricts the lifter galleys to 15psi and the drop in volume that comes with restricting. The JDM HLA that some people use to try to fix this, simply dumps the excess into the head. the Kiggly unit keeps it in the pan.

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You need oil pressure to keep up, and its tough to maintain on the stock hardware.. especially with big bearing clearances. Post 1995 7 bolts also have their oil squirters fed from the same vein that feeds the mains/rods.

It helps with crank case evacuation as well. Adding a dedicated drain, like -12 from the head back to a balance shaft hump helps too.

 

[Cdc1221]

That part actually didn't cross my mind. Guess it's the same concept as why a turbos compressor is most efficient at a certain rpm, and once it exceeds it, it's fighting itself to do more..

You say youre trying to exceed 225. Why couldn't you do a custom gearbox with a much taller gear ratio to achieve it?

I guess i just need to climb back into the box for a while until my financial situation changes some . Thanks for the explanation

 

[LandSpeed-DSM]

Well, I have a few years before then realistically. And on a 26" tire, with the FWD Final Drive Ratio and 5th gear I should have plenty of overhead, but I don't know what sort of tire slip to expect on the salt.. or how much being at altitude with an even greater DA will move my powerband to the left.

It's basically contingency planning in case I have to make a go of it in 4th instead of fifth for better gearing.

A 26" tire whether its a skinny LSR tire or a DR/Slick in 235/60-15 on a 1G FWD MT can do 200mph in 4th @ 9500rpm.. 5th will do it at only 7900rpm.

My pavement wheels/tires are only 24.85 though, 225/50/16. My first real long course runs will be on pavement on the shorter tire, which will need more rpm, toward the end of summer this year.

I am hoping to make some 160-170 passes under the ECTA while sorting out some bugs. Next year I hope to tech for 200 and then make at least a 201 pass at the Ohio Mile or somewhere comparable.

Food for thought, given ~3-4 miles of flat straight paved road, it takes on 530whp to do 200mph in a 1G DSM.

Making the power to hit those speeds won't be nearly as hard as building a car to pass SCTA Technical Inspection for a class with an existing record of 227.xxx

Custom gear box is out of the budget for at least a few years while I am sorting the safety stuff.

I expect to strip a few 4th and 5th gears in the mean time. I have a TRE Gearset in the Trans now, and I plan on modding the case to dump fresh oil over those gears and they have been shimmed with the hope of keeping as much tooth contact as possible even at those shaft speeds and loads..

 

[Cdc1221]

Is that a standing mile run, or just overall Bonneville type top speed runs that you're going for? Too bad i dont live closer. Id like to pick your brain more . Something about shooting for top speed seems alot more intriguing to me than going a quarter mile at a time, even if i were just a guy helping develop the car to do so

 

[LandSpeed-DSM]

Both have their challenges, thats for sure.

Starting with the quarter mile stuff at GLD for shakedowns.. then my main event for the year is the half-mile shootout in June.

If nothing catastrophic breaks and there's room in the budget for more safety equipment that I can tech for 175mph.. I'm going to the ECTA Mile Event in Ohio.

Bonneville/Wendover (SCTA) trip is on my planner for 2016 at the latest. I'd really like to go to Loring, but that may be yet further off still. By then the class record will have likely been beat again, and there will be yet more technical scrutiny and safety equipment added to my check list.

You have to tech to the Record for the class, every time its beat things change

I have a lot to learn as well.

 

[Diamond Star Werks]

Want something diff? mount turbo out of engine bay somewhere near the rear, but on a cut out from the main exhaust line. Use a cut off that completely changes the exhaust direction. So you look nt under the hood then by one switch you become turbo. Intake piping would hinder the nt look though which I thought about while writing this

Side more I still have an 11k goal and the fp black will be my turbo to wind out

 

[Diamond Star Werks]

Land speed couldn't you use a pump to dump oil on the gears to keep then cool? Attach it to the bottom of the pan and dump through the top if the trans?
And I don't guess there is a, way to change your final drive instead of custom gears?

 

[Cdc1221]

Damn so basically you have to strip the car down to a rolling gas can, then add in the safety equipment...
im not even gonna ask whatall that involves

 

[LandSpeed-DSM]

Want something diff? mount turbo out of engine bay somewhere near the rear, but on a cut out from the main exhaust line. Use a cut off that completely changes the exhaust direction. So you look nt under the hood then by one switch you become turbo. Intake piping would hinder the nt look though which I thought about while writing this

Side more I still have an 11k goal and the fp black will be my turbo to wind out

11k rpm 2.0 will be choking well before 11k on the Evo9 Black. Too small on both the compressor and turbine side for that much engine demand and exhaust gas flow. It's only a ~70lb/min turbo in a bolt on Evo housing.

It's falling off before 8k on most dynosheets I've seen including the ones on the FP Website. The Torque curves tell the story:

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Land speed couldn't you use a pump to dump oil on the gears to keep then cool? Attach it to the bottom of the pan and dump through the top if the trans?
And I don't guess there is a, way to change your final drive instead of custom gears?

That's basically the plan, using a tilton diff oil pump to drop a stream of oil right on them.

The Final diff is fine as is, the FWD is pretty tall at 4.2x. I have a Quaife LSD, and whatever axle gear available would have to work with it.

I would like to swap a .666 AWD MT 5th in eventually. But it's still a stock gear. I'm wondering if I could get a straight cut 5th made, with dog engagement..

Damn so basically you have to strip the car down to a rolling gas can, then add in the safety equipment...
im not even gonna ask whatall that involves

More or less. Weight is your friend for stability. And all the equipment helps. I'll be adding 10+ gallons of coolant capacity to keep things happy. Then there's all the cage work, roof rails etc.

It's a big project, and I have no sponsors at the moment. This is purely a personal engineering challenge. If I happen to be competitive in the end it would be icing on the cake.

Bonus: The car is staying street legal, including a passenger seat. Possibly a radio too haha

 

[Cdc1221]

Be something else to drive around in a 200+ mph car on the street that doesnt say ferrari on it .

If his comp ratio is high, that turbos efficiency range could be stretched out some because it would require less airflow. But i guess thermal expansion would be about the same so it'd still overrun the turbine

 

[LandSpeed-DSM]

Well.. no, because the motor would be cammed to run out to 11000rpm, so as a result VE at that RPM would be high and as a result the Engine Demand Flow is going to swallow well more than the turbo can provide in terms of volume and massflow.

This is independent of compression ratio.

Compressor efficiency is also independent of either of those things.

Also a higher effective compression means there is less heat energy wasted to the exhaust.. because it is being used in the combustion chamber.

Even with poor VE.. in the 70% range.. 2.0L swept displacement 4-stroke at 11000rpm is too much for that turbo.

 

[Cdc1221]

Well that makes sense. I guess i need to quit thinking so much and start small and actually learn a little more. I know the basics of alot, but an expert of none of it

 

[TurboLaserRS]

I'm not adding much to the discussion here but I just have to ask. What kind of cam would you even have to run to be pushing 12,000 RPM??

 

[Diamond Star Werks]

Well actually I was planning on it for a destroked 2.1 long rod engine.
Take my 64 from my spyder use the 88mm crank and use alum long rods and stroker pistons to allow for 168mm rod length Butcher the crank, lightweight billet flywheel, twin disk clutch, ATI dampener, dual springs with chromoly retainers, dry sump...$$$$$ long time from now though

 

[Diamond Star Werks]

Well.. no, because the motor would be cammed to run out to 11000rpm, so as a result VE at that RPM would be high and as a result the Engine Demand Flow is going to swallow well more than the turbo can provide in terms of volume and massflow.

This is independent of compression ratio.

Compressor efficiency is also independent of either of those things.

Also a higher effective compression means there is less heat energy wasted to the exhaust.. because it is being used in the combustion chamber.

Even with poor VE.. in the 70% range.. 2.0L swept displacement 4-stroke at 11000rpm is too much for that turbo.

so a 2.1 would increase this factor and overrun the turbo much sooner wouldn't it?
I was gonna use an 11.5cm^2 housing with it but I don't know if thats bigger or smaller than fp's. I wonder where the turbine would run out of steam given a larger turbine housing.

 

[LandSpeed-DSM]

I'm not adding much to the discussion here but I just have to ask. What kind of cam would you even have to run to be pushing 12,000 RPM??

A real blocky one. Think in the neighborhood of TX294HL, Custom GSC S3 (What I'm going to be using), FP5R/11R, Custom Comp cam.. that sort of thing.

Good amount of duration, and a lot of lift because the valve events are occurring VERY fast. Pressing the limits of our valvetrain geometry.

Problem is you start bouncing valves off seats and goofy harmonics come into play, even well before 12k.

Keeping rockers intact appears to become problematic.

so a 2.1 would increase this factor and overrun the turbo much sooner wouldn't it?
I was gonna use an 11.5cm^2 housing with it but I don't know if thats bigger or smaller than fp's. I wonder where the turbine would run out of steam given a larger turbine housing.

Well, if its actually around 2.1 or closer to 2.15 you are adding 5-7% more displacement, and you would choke on one side or the other that much sooner.

You would have to get a hold of FP for actual numbers if they would even provide them, but I would not be surprised if the housing and wheel are both about completey tapped out around 68-70lbs/min and 8-8.5K on a high VE 2.0

The turbine wheel is pretty small its' self. A bigger housing would only help so much up to a certain point.. They seem pretty well matched as is.

 

[TunaTalon]

There are several good points on this thread about how to get higher RPMs. But not a post about how to get more air through the valves. The absolute limit of horsepower for any version of the 4GXX engine is sonic air flow through the valves. The valves will reach sonic flow at the same CFM regardless of the RPM.

Race engines have over square engines where the rules limit the displacement. For any displacement, the bigger the bore the more room there is for valves. Longer strokes for the same displacement means smaller valves.

If you need higher RPMs for higher trap speeds or just to enjoy hearing the Eagle scream then longer rod ratios and lighter reciprocating parts are the way to go. But this olde phart chose more stroke for more street friendly torque. Your mileage may vary.

 

[LandSpeed-DSM]

I was waiting for that to come up. So here's what I have done to address that:

I have a 1G head, opened ports, bowls and throats with larger valves. Greater volume/cross section = lower charge face velocity.

One thing you are neglecting is the speed of sound is dependent on the density of the medium it travels through.. at 320-340 Kelvin (116-152F) intake air temps and 40+ PSIg/55+PSIa .. the speed of sound has increased considerably.

Add to that the factor of relative humidity and account for the amount of water/methanol and E85 I am injecting and you can see where this is not as much a concern as you make it out to be:

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Speed of Sound is found by:

[c= √(γ(p/&#961)]

(Pressure/Rho) is a constant admittedly.. cancelling out the change in pressure, and we are treating air as an ideal gas.. so you'll find temperature and humidity are the main effects. Both of which are to my advantage in this case. Adding ~1L/min water and meth mix to 90+ lb/min airflow and the complimentary dose of E85 at .75 lambda makes for a drastic increase in density as the charge enters the ports.