Not any engine, but any engine that is prepared by any place that doesn't do it to race engine standards. The overwhelming majority don't.


Again, why cater to novices in the advanced section? Are you saying the only way you're going to post non-novice-level stuff is if the advanced section is a private section with only people that have passed some sort of advanced test admitted?


OEMs invest in initial design, and lots in castings and tooling, but once that is done the mass produced engine is cheap. They are designed to be cheap. Compare the stock block and its tolerances to one prepared by a good shop. Compare the quality and cost of stock and aftermarket components that many of the people here buy. There is no comparison. If I build a real high performance 4G63, and compare it to a stock 4G63, you will find that the amount of money that the companies whose products I use, have spent a lot more money than the OEMs - in the areas of design, casting or forging, machining, finishing, assembly. There is no way to argue this.



Yes you're exactly right, you are not my room mate. I wasn't calling you a liar. I was making the point that title and status do not matter and that what a person has to say, how much thought they've given it, whether they're earnestly trying to accomplish something good, matters. Saying something false without thought is not as bad as lying. Neither is purposely saying something false purely for effect, but it is a lot closer to a lie.
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Evodan and GTP, thanks for the comments.

 

Exactly, please let Homemade know that they have exceeded 24m/s long ago. My original reply was to him, about comparing his sportbike engine to F1 without knowing F1 cylinder geometry, or the rules that almost define it in those types of engines (large flow area requirement).

 

I didn't they that they hadn't...just saying what my 250rr motor does...I don't recall stating what mean piston speed an F1 motor turned...all I stated was a rod ratio and that has nothing to do with speed other than both use stroke to give a value...
I agree that you can spin past 30 m/s and have the motor come together but then is it worth the cost, extra weight of the beefier components, frictional losses and driven component losses do to the higher rpm's? Are the VE's at that rpm still showing a gain or is the torque curve falling of the face of the planet?...

for this arguments sake is the average enthusiast, who is 99% of the time buying parts off the shelf, safe to spin their parts to the "pushing" the edge limits (I consider F1 the limits of motorsport engineering personally)....?

I think we have seen they can hold together but how long is the fuse on the time bomb. I just think it unwise to boldly state what people don't know for sure to be safe. I always waiver towards the safe side when advising on things I'm not certain of.
that is the only reason I stated it. I'm all for educating the common enthusiast as long as they are willing to learn. I do it at my shop all the time.

 

You were trying to draw parallels between it and F1 engines, implying that F1 MPS s are lower than they actually are. If you brought it up for nothing, then why do it when it is irrelevant and has no bearing on the discussion?

Why state the obvious, especially when I have never said anything about rod ratio being related to speed?

People will pay lots to be faster, to win, to feed the ego.

Why do you assume that frictional losses are directly related to MPS? Are you forgetting that it is all forces and cycles? I can build a 25 m/s engine that has much greater friction levels than a 30 m/s one.

Are you assuming that stroke has to be kept constant in raising MPS?

If VE and torque were falling off the face of the planet, Cup car wouldn't be running near constantly at the ~27 m/s MPS range they do, and neither would other 30, 32, and try 38 m/s, touching over 39 m/s MPS race engines run to those ranges.

Don't forget VE is heavily dependent on the heads and flow areas and tract design on both sides of the cylinder and need not be tied to MPS. If VE is good, IMEP is good. If IMEP is good, BMEP is good. The exception is where high FMEP kills it. But don't assume that high MPS equates to high FMEP. Stroke, hence engine speed, are large factors.


First of all, there are many who build high dollar engines. Second, many shelf parts are high quality parts and can do much greater things than you most imagine if enough planning and preparation is carried out. Third, there is no rule saying you have to keep catering to the poor, the stupid, or whoever else is looked down on. Hiding behind those excuses after making silly assumptions or plain errors is very lame. One pushes as much as the budget allows. Push how much? Study the factors and do own calculations and comparisons. Don't parrot the same MPS figures that have been going around for years, without any understanding of why they exist or if they're even a real limit at all.

F1 is not the limit, it is the current pinnacle. Budgets dictate the limits and they grow and shrink all the time. Engine wise with all the rules and freezing, MotoGP is set to overtake F1 tech wise. This is unless there are subsequent rule changes there too to contain cost.

I've yet to boldly list a cetain MPS as safe. It is unwise to boldly state a low MPS a limit. It is you guys listing absolutes, not me. I only point out that there are 27, 30, 32, 38 m/s race engines out there, running, winning, not experiencing the sort of problems you guys claim exist at 25 m/s and 30 m/s. Just look at what's happening in real life and then go figure out what allows them to do it. I can tell you it has much more to do with geometry and physics, rather than money.

What I believe it is, is too many people looking at F1 turning 25m/s and then immediately thinking "well that's the pinnacle, so that MPS must be the limit, with everything else falling below it". Just take a look around and follow numbers, not assumptions.

 

So Shaun, you seem to be knowledgable, but have yet to really add anything except to argue that others are wrong. Let's get back to the original question and see what you have to say. What is the rev limit of the 4G64?

If we could all stop this silliness and focus on answering the original question and supporting your answer, we might all learn something.

So how about this proposal, no more quote - counter quote. It is futile, pollutes the thread and really doesn't help.

 

I don't know which is worse, desiring a quick and easy (but wrong) answer, or giving a quick and easy (but wrong) answer.

There is no answer to a question that lacks so much detail. Now, even if the details were provided.. and I can think of perhaps 15-20 off the top of my head just sitting here, who do you think would be in a position to authoritatively answer the question, and why? What kind of resources would he need to have had access to? How much time and money would the person have spent finding out? How much should he charge you?

 

On the quartermile, rev limit 8k from 1-3 gear, 8.5k 4th gear. Depending your mods and the weight of the car and traction, mid to low 10s is easy.

 

See Shaun, you've done it again, posted a whole bunch of nothing. Of course there is tons more information needed, but sometimes this information isn't avaliable and a general answer is needed.

A specific example; I know someone that recently purchased a stroker EVO from a dealer that had no information on what was done to the motor. It was confirmed to be a stroker because it had the 4G64 crank. So what do you tell someone like this about how high to rev their motor, "sorry, but there isn't enough information"? "Tear everything done and I can give you an answer", yea, that's an option. In this situation, Ted's answer is sufficient. Is it exact or precise, of course not. It was posted as a general guide and that is exactly what the guy I knew needed. He settled on 7500 rpm. Could he rev it higher, maybe, but as you noted, a bunch more information is needed to get an more precise answer. However, 7500 rpm should keep his motor together.

Nothing personal, but you seem to have an agenda in this thread and it doesn't involve helping anyone.

 

In the example you list and in all other cases, it will take far more than a spec list, far more than tearing it apart for a definite answer. Some people are too insecure to say "I don't know because I don't have the knowledge, experience, access to resources to give you a definite answer."

Those with more experience than the former, and who are just as honest might say "From my experience with these type of engine, and from what you have described, I would say somewhere around AAAA RPM , or the XX to YY m/s range. This is just a rough estimate from what we've learned racing, and how we build, tune, run these things. But everyone does it differently so you may get different answers from others."

Going a step up and being just as honest, others will say something like "We've had experience designing, building, field and bench testing all sorts of engines, but not this one or anything close to this kind of geometry and design, so we have no answers at this point. It is easy enough to find out though, if you want. We will model so we can start actual tests reasonably close to calculated limits. We will then build and test a few engines at different levels in controlled conditions - all eventually to destruction or to mileage and loads exceeding expected, to find longevity@output@conditions distribution and the weak points, and report on all the other components post-run. If you want to find out for just this combination, then we will build and test just 4 of them. It will take us around 2 months, and we will charge you $YYY,YYY. If you want to develop the combination to reach a higher performance and/or longevity target after first round results, we can suggest changes based on the results and build another 2 or 3, each to different but higher specification, that will meet or exceed targets. This will require an additional 2 months and $ZZZ,ZZZ. "


None of either 3 groups, if they're honest, will blurt that race industry consensus is that at 25 m/s component life takes a dive, and at 30 m/s ring seal efficiency take a dump, or that F1 does this and that (and inaccurately so). It is not the race industry consensus.

There is a big difference between saying the above, versus "looking at existing examples, and at your stroke, revving no higher than 7000 RPM should allow your engine to make good amounts of power and still be very safe.

 

Just stop.

 

i wonder if cosworth did what shaun said.

they have seriously nutty rev limits tho.

 

ok, shaun...I didin't seem to clearly get my point out as I suck at doing...

I'm know that VE's are heavily affected by what the heads can and more importantly the cam/valves will flow at a given engine speed...also part of the reason I brought about the frictional losses...I was really arguing for a shorter stroke and longer rod allowing lower frictional losses, more constant flow velocity (higher VE's) and higher achievable speeds as the max velocities and accelerations are lowered and there for the stresses on the internals (neglecting weight gain as it is normally minimal in my design lower)...not saying what is or isn't possible...In this mind set you are right, FMEP would be the killer so long as IMEP and BMEP are good...

cup cars, F1 and other racing organizations are being or are now limited to engine speed to keep them from long rodding and big boring there engines.

as for the driven component losses, I wasn't reffering to stroke but everything else in the engine that is spinning...oil pump, water pump, cams, etc...they increase drastically with speed as you well know if you have seen spintron values (I'm sure you have).


as for comments on customers and products, you are right...people are willing to dump tons to be faster and many do it without being told what could happen or what the trade offs are. Some really don't care and just want to win while others want something reliable yet fast.

yes, many of the shelf products are great but coming from the engineering side of the house I really don't trust or greatly trust any product that I don't know the numbers for...or the design specs/criteria. I've seen many products that are just given the dimensions of the factory components and are just built. Some of the aftermarket piston designs just blow my mind. Guess that is why I'm having my own pistons and rods made....does make things more costly though.

 

if they did this then that would make their price kinda... worth it :\

 

This almost always does not happen in real life once you normalize for throughput and drop engine speed on the longer stroke engine. I'm not going to discuss this here again because there is more than one thread that has been left to waste with no conclusion. All this has already been covered and I'm not going to explain it again.

That's not what I said. FMEP is not always a killer unless inertial loads are high. Inertial loads come foremost from engine speed.

I really don't mean to be rude Homemade, but you really need to stop saying things like this because is simply untrue.

Limiting engine speeds is done to reduce development costs to even the field. It is not done to directly limit them from running long rods or big bores. A simple bore rule or rod dimension rule does that. F1 has existing bore rules. IIRC neither Cup nor F1 has a long rod rule, but Cup has component mass rules, again to limit development costs to a degree. The sanctioning bodies are not concerned with whether you run a short or long rod, because it is very distantly related to safety and cost (their primary concerns). This is why you find component mass, CG, engine speed, bore rules, alot more than individual component dimenions. In most cases the bore limit sets your stroke, and then with stroke and compression heights, the block height sets rod length. The block height is also limited by engine CG height rules (in conjunction with natural or sanctioning body V angle rule), or casting modification rules.

How fast the auxiliaries turn is loosely related to engine speed through stroke, but it is directly related to engine speed. So expressing concern about mean piston speed as it relates to auxiliary speed is imprecise.

Yes so we can just discuss issues and list considerations and let each group decide, instead of giving them only what we think they want. Especially in the advanced section. It's not a matter of we're up here, they're down there, we decide what balance they should have and we dish out the vague guidelines.


If you are building engines that require components exceeding what top tier component makers can supply, then you are building something uncommon like a high performance vintage engine, or something current but extremely high performance.

I'm not sure which piston companies products you were looking at that were so shocking or how you can give them piston specifications without yourself going deep into piston design details. For example, who is getting your pistons done and what kind of breakover did you suggest based on what about the engine and how many breakover options did the company offer?

 

once again I fail to say what I mean...what I meant is has given them a "roof" to which a certain rod ratio "X" and big bore of "y" with short stroke "Z" (loosely said for example/not literal) has become a cap as longer stroke "K", shorter rod ratio "I" and smaller bore "j" for the limited displacement would now become a more ideal motor. Yes it is all to keep cost of R&D as practically every race league tries to do.


I wasn't trying to reffer it to stroke and my point of making this comment is really off track with the purpose of the thread so ignore that it was ever made. I was reffering engine speed and not mps.


[QUOTE=ShaunSG;4046278]Yes so we can just discuss issues and list considerations and let each group decide, instead of giving them only what we think they want. Especially in the advanced section. It's not a matter of we're up here, they're down there, we decide what balance they should have and we dish out the vague guidelines. [quote]
quite true and didn't mean to come off as I'm up here and they are down there as I'm certainly not up "there"


many of the off the shelf pistons are just replicas of the factory pistons which in many engine cases isn't suitable for making big power or high boost. Many of the them have horrible quench pads, thin ring lands and some just poor design with many sharp edges for hot spots. I'm a fan of few off the shelf pistons. Besides, with the engine I'm building, no one makes a piston with the right combustion chamber footprint, valves reliefs, decent quench pad, right compression height, CR and bore....I had discussed initial designs with JE and Wiseco and quite certain I'll be running JE's.
Yes, the engine hasn't been done before so that would fall under uncommon.


so how many people have spun the 100mm crank past 9k?...video or personal experience accepted...also curious as to what rods and pistons as the pistons have a compressed-compression height which brings about the problem that I was told (apparently not an issue) with rings and ring lands starting to fail...what really is the limit?