LP Connecting Rod Discussion

[Curtis]

GP Toyota not only had prep 1 rods it had webers with individual runners which = torque. I am not familiar with the Toyota specifically but some downdraft carb on poorly designed plenum engines have intake pulses that confuse each other. Solution is often low/no overlap which enables you to make up for the lack of torque with rpm and resultant HP. If an engine like this rods might be needed to run the kind of rpms needed to keep up or for that matter make anything like the kind of power you think it should.

Besides the Toyota doesn't need the brake upgrade it recently got if it can't get up any speed

 

[RonInSD]

My personal option is that if it is one motor having the trouble then just that one Prep 2 car should be allowed the rods maybe with a 25 or 50 lb weight increase. Spec line changes are allowed for a number of different cars why not this one.

Every motor has a weak link. For mine it is rocker arms and oiling system. I have rocker arms that have been clearanced, shot pended, and polished. They are a wear item and I replace them after about 20 hours of run time. I feel that sometimes Prep 2 should be allowed dry sump but limit the size and number of scavenge and pressure stages. Cost are close by the time you include custom oil pans with trap doors/kick outs, accusumps, and better then stock oil pumps to make wet sump work.

But I also worry about rules creep and then we are back to Prep 1 for everyone. Once aftermarket rods are allowed across the board, everyone will think it is what you need to build a Prep 2 motor. How many people will we scare away because of the cost of racing Prod? Everyone talks about loosing racers, we also have trouble getting new ones which is why Limited Prep/Prep 2 has brought up.

 

[zChris]

Ron, Tom Campbell, Serge Lentz and myself all blew motors due to rod failures with the FP Miata. Mine had expensive new stock rods that lasted 1 lap and Kaboom. You want to know a way of chasing poeple out of a class fast, this is the recipe. With the Miata its an ongoing problem. I had fun racing in smallbore. It just cost to much. GT3 will be cheaper. So thats were I headed.
Chris Howard

 

[Brian Linn]

Ron, Tom Campbell, Serge Lentz and myself all blew motors due to rod failures with the FP Miata. Chris Howard

+1 - I lost an engine in '09 due to rod failure.
I don't take my RPM past 8000, on purpose. Not much power up there beyond 8k. However, if I miss a shift here or there, I know that the stock rods don't like that much and you only get a few before they stretch too much. I had my engine rebuild recently because I knew I had a ticking time bomb, but it was still making great power otherwise.

The cost of a set of prepped stock rods is not significantly cheaper than a set of 'real' rods, especially when you factor in the rebuilds. I know I'm repeating what many have already said here. For my car, I wouldn't see a performance gain, but would see a durability gain. I did write a letter when they asked previously.

 

[James Rogerson]

Any rule change for durability should be across the board or it isn't about durability it's about making "my" car faster/better.

Just saying.

James Rogerson
Honda limited prep with stock everything except cam and pistons.

 

[JessePrather]

The last thing I want to see as an engine builder is one of my engines blown up because of an inferior part. I've always been and am still in favor of allowing alternate ferrous material rods. For an LP engine it's not a cost savings to require stock rods because of what has to be done to make these work at the rpm's we run the engines at. We rev the engines to the max power they will make. With 10:1 compression and .390 valve lift, we peak out between 7800 and 8k rpm's. For a 3.29 stroke it's not a bad deal. I've tried many different camshafts and the limit of the engine for rpm must be the throttle body or stock valve size because they just don't make any power over that. The only two failures I've had are with overrev's and it's a shame because with a proper rod the customer wouldn't have blown up his engine and/or need to replace the rods at a high cost between prepping a new set much less the cost of taking the engine apart. It's crazy. I think we should limit compression, valve lift, and porting and leave it alone. Allow the alternate rocker arms, rods, etc. that guys need to make these more reliable. 15:1 compression engines and unlimited valve lift is over for the vast majority of the cars in production these days. Nobody wants to go through that hassle or unreliability. It's what killed production in the 90's.

Just my opinion here so don't expect me to get into a pissing match with anyone.
Thanks!

 

[kruck]

My opinion is, that all cars have their warts and their weak spots. If you miss a shift in a Honda, you drop the head of a valve, and your engine goes kaboom. So along the same line of thinking as being presented in this thread, I should be allowed titanium valves, springs, retainers, right? Nope, because that's how rules creep happens. Then another make who's rods are the weak spot, they'll want that. Then another who's followers are, they'll want that. And if you allow one, then you'll have to allow the others, all the way down the line. Before you know it, you're damn near at full prep Prod again, at least in regards to the powertrain.


I also hate to say it, but really, if the reliability of a limited prep Prod engine is enough to drive you away from Prod, then this hobby might not be for you. They're machines, that we're beating the crap out of. They're going to break......especially if you make a mistake.


The dead horse of this whole topic has been beaten so badly, that it's already been turned into glue, yet absolutely no new evidence or reasoning for why this is a good idea has been brought forward. I really don't know how you could better define rules creep. Competitor X says "I can do this to my car, and it'll be easier, faster, and more reliable!". Competitor Y says "Well, if Competitor X gets that, then my car should get this thingy, because it too will make my car easier, faster, and more reliable!" Wash. Rinse. Repeat. Insert full-prep. Insert GT. Whatever it is you're trying to solve, will just raise something else to the surface, and by that point a precedence has been set to allow alternate parts in order to solve "problem areas", and by that point.......cats really hate being stuffed back into bags.



I'm also with Jessie, and this is my opinion, which I think I'm still allowed to have in this country.

 

[disquek]

If your car were properly limited from a volumetric standpoint, those TI valves, heavy springs, etc would be of zero value to you. You'd be wasting your money.

The idea here is to properly limit the cars HP potential using the right tools (not rods) like choke size, valve size, cam lift, compression, etc.

It amazes me that local circle tracks have solved these issues for decades, but us "smarter" road racers still cant grasp the idea of how to limit horsepower and make reliable engines.

Making the cars more reliable adds value to the class by making them more fun. There is your good reason.

Maybe you missed the part where Chris went from an existing FP miata to a built from scratch GT3 miata BECAUSE IT WAS LESS WORK and where Jessie said he was in favor of the idea of allowing rods.

-Kyle

 

[Gary Wittman]

If your car were properly limited from a volumetric standpoint, those TI valves, heavy springs, etc would be of zero value to you. You'd be wasting your money.
-Kyle

Kevin just stated that the valves where the weak link in the Honda engine. Ti valves would probably solve that problem. Other engines have rods as the weak link and after market rods could solve that. I guess you are saying that is is OK for the Honda to blow an engine because of valves but it is not OK for the other cars to blow an engine because of rods.

This is the problem with rules creep, once it starts it becomes a slippery slope. How can you justify one improvement and not others.

 

[JessePrather]

If your car were properly limited from a volumetric standpoint, those TI valves, heavy springs, etc would be of zero value to you. You'd be wasting your money.
-Kyle

Kevin just stated that the valves where the weak link in the Honda engine. Ti valves would probably solve that problem. Other engines have rods as the weak link and after market rods could solve that. I guess you are saying that is is OK for the Honda to blow an engine because of valves but it is not OK for the other cars to blow an engine because of rods.

This is the problem with rules creep, once it starts it becomes a slippery slope. How can you justify one improvement and not others.

Very true Gary. I can see both sides and would hate to see rules creep again in production.

 

[disquek]

If your car were properly limited from a volumetric standpoint, those TI valves, heavy springs, etc would be of zero value to you. You'd be wasting your money.
-Kyle

Kevin just stated that the valves where the weak link in the Honda engine. Ti valves would probably solve that problem. Other engines have rods as the weak link and after market rods could solve that. I guess you are saying that is is OK for the Honda to blow an engine because of valves but it is not OK for the other cars to blow an engine because of rods.

This is the problem with rules creep, once it starts it becomes a slippery slope. How can you justify one improvement and not others.

Please please please stop putting words in my mouth. I said nothing of the kind.

I'm not sure why typing this again will help, but here it goes.

Limit the horsepower using volumetric efficiency (cam lift, valve size, etc). Allow competitors to replace common failure parts with good solid race parts that last a good long time (the right tool for the job). Be smart. Write the rules so that this doesn't result in light weight rods, etc. This will result in good parity and less money spent on blown motors or timed out parts.

So ... in the example of the Acura, the TI valves would not help him because the limiting factor WOULD NOT be valve failure. It would be volumetric efficiency. If it needs TI valves to live, then it should get TI valves. But I hope you understand that TI valves are weaker and last less time than steel valves. So maybe either you or Kevin should reconsider the example.

I think in Kevin's example he's saying that valve float is limiting his HP. Valve float does not typically blow up engines. Also, valve float is a stupid way to limit HP.

-Kyle