Drilling Out connecting Rods

[Bam Bam]

I was talking to a lot of teams last year and heard that one team got MASSIVE acceleration gains from drilling out there connecting rods
Does anyone have a HDTC (heavy duty transient cycle) dyno run indicating the acceleration gains before and after.

I know it may sound like a bad idea but the bikes are engineered for 14 500 rpm and many many kilometers all which will never be seen in FSAE. Apparently they had no reliability issues and had running it for a few weeks before the competition.

[Bam Bam]

I was talking to a lot of teams last year and heard that one team got MASSIVE acceleration gains from drilling out there connecting rods
Does anyone have a HDTC (heavy duty transient cycle) dyno run indicating the acceleration gains before and after.

I know it may sound like a bad idea but the bikes are engineered for 14 500 rpm and many many kilometers all which will never be seen in FSAE. Apparently they had no reliability issues and had running it for a few weeks before the competition.

[FFgeoff]

please dont drill a rod out to save weight...

there are other ways to reduce reciprocating masses, this is one of the worst ive heard.

we are the music makers and we are the dreamers of the dreams
--willy wonka

[Sleeque]

A guy I know, a multiple champion, kept half a conrod nailed to the wall above his workbench to remind him of the stupidity of his youth.
The conrod had broken neatly through the drilled hole he put there to reduce the weight !
Do not drill conrods unless you want your cylinder block sawn in half with terminal suddeness!
Sleeque

[Engelbert]

Do any teams make their own con-rods ? If so, what of ? And what level of improvement was associated with this change ? pistons/modifications ? other internals ?

[Matt_L]

Drilling holes in the connecting rods is definately a possibility, however the reliability is jeopardized.
A good friend of mine did just that as well as lightened the crank as light as possible and take weight from the pistons. He had no problems at all, but the engine was only used for qualifying sessions. His laptimes were upwards of 1 second per lap faster with that engine.
If you have the resources and capability, a lightened engine as such, could be a big benefit in the autocross runs at the competition.

Matt

[James Waltman]

Engelbert,
Our V8 had connecting rods that we made. I know that it doesn't strictly apply to all of your questions here but it can be done. It had to be done to make the correct displacement so gains/improvements don't really apply. I know that there was a problem with one of them during dyno testing but I don't know why it failed (I don't think it was the material or design – possible assembly problem?). I think that about 10 sets were made (8 rods per set). The alloy used was 7150 aluminum. There are some pictures of them on our website in the Viking XXX photo gallery: http://dot.etec.wwu.edu/fsae/v30/v30pics.html

Picture 037 shows a rod with piston. Picture 011 shows the effects of a grenaded rod and its complimentary damage to the oil pan. Some of the other pictures on the site also show the connecting rods.

James Waltman
waltmaj@cc.wwu.edu
Formula SAE
Vehicle Research Institute at
Western Washington University

[MikeWaggoner at UW]

If you really wanted to save weight, going to aluminum or Ti connecting rods would be a good step. Aluminum ones will need replacing often because of fatigue, but there's basically no downside to Ti.

Western Washington University FSAE
dot.etec.wwu.edu/fsae

[EliseS2]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by MikeWaggoneratWWU:
If you really wanted to save weight, going to aluminum or Ti connecting rods would be a good step. Aluminum ones will need replacing often because of fatigue, but there's basically no downside to Ti.

Western Washington University FSAE
dot.etec.wwu.edu/fsae<HR></BLOCKQUOTE>

Well except the cost of the ti rods.

[Bam Bam]

don't look now but most stock con rods on bike engines are some form of aluminium or even Ti. I think either the gsx'r or the r6 has got ti rods as a stock feature.

BTW I did a bird FEA project on how to properly drill out a conrod, it can be done to actually relieve stress in the engine compartment.

stil that's FEA...and I trust that about as much as my ex girlfriend.

It turned out the savings in recipricating inertia would amount to a similar weight as if you decided to shave all your leg hair before the event.

Which I heard other teams doing and getting MASSIVE horsepower gains.

See ya at the competition

...showin off your shiney legs.

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bam Bam:
don't look now but most stock con rods on bike engines are some form of aluminium or even Ti. I think either the gsx'r or the r6 has got ti rods as a stock feature.
<HR></BLOCKQUOTE>

I wouldn't say most. The CBR rods are definitely ferrous.

-Charlie Ping
Auburn University FSAE 1999-present

[Spike]

There are NO stock bike with Ti rods or Aluminium for that matter. All modern "sportbike" motors use ferrous rods. A set of Ti rods is over 2k USD. SO it might be awhile before we see Ti rods as a stock production item, and an even longer time before they will appear on a 600.

[MikeWaggoner at UW]

The stock for the rods isn't that expensive, and aside from learning to machine Ti they don't take long to machine. I guess I'm just used to think of everyone having access to CNC mills... I think if you really wanted to you could also make decent ones by hand, but it'd take a damn long time... That said, they're not that complex a part.

Western Washington University FSAE
dot.etec.wwu.edu/fsae

[Spike]

They are a simple part to machine. Yes it will make the engine more responsive. But the $$ to difference ratio is way to high.

[Travis Garrison]

Cost? What cost? Seriously, if you have access to machines they cost next to nothing, if you have money and no machine access they might still be worth it since you wouldn't take a hit in the cost report for rods...

[Spike]

Have you price out Ti plate before. Cost next to nothing give me a break. Ask your schools machinist about the workability of Ti. You will spend big money for all the cutters that will wear out after 30 minutes of milling. Trust me I know what the difference will be between stock rods and a set of Ti rods. And for the money you won't be happy. I race bikes, I know what makes a difference and what doesn't. Removing the charging system with make a way bigger difference then Ti rods. I don't think there is a rule against removign the charging system. As for the battery not lasting I can use one battery for 2 20 minute practice sessions and 5 sprint races (8laps on a 2mile course) without it causing a problem. And that's also running my datalogger off it.

[Travis Garrison]

I don't believe I said anything about ti...for these bikes I would think al would be a perfectly acceptable, albeit consumable, alternative...

It is after all a pretty short event...and the motors aren't exactly making tons of power...

Travis

[James Waltman]

I read through this before I posted it and it kind of reads like a flame. That was entirely unintentional. This is all meant to be in the spirit of a good debate.

Spike,

What is a school machinist? It is a foreign concept to me, could you tell more about it? Our team members are our schools machinists. Mike Waggoner and Travis are competent CNC machinists. Our team members have gotten very good at machining because it is something that we do extensively on our cars. It is not unusual for the professors to come to us with questions about machining. Titanium certainly does cost more. It does wear tooling faster but I am pretty sure that it is not as drastic as you think. If improper feed and speed are used then the tools will certainly wear out very fast but that is true for any material. The price of Titanium stock is not that unreasonable if you compare it to the cost of replacing the rods with a stock set. Our local Honda dealer wants $132 each for stock replacement connecting rod – $530 can buy a lot of stock and tooling.

With that said I agree with the post Travis made just above this one – aluminum may be the way to go.

The cost to difference ratio is pretty high but I don't like to look at things that way. The things one learns during the design and manufacture of are very valuable. This is an engineering competition for students. What do you learn by removing the charging system?

James Waltman
waltmaj@cc.wwu.edu
Formula SAE
Vehicle Research Institute at
Western Washington University

[Ian]

If someone is serious about Ti they will want to get rods that have been machined from a forged blank. Also, they will work harden just like aluminum unless a large rod is used.

Ian Dawkins

Ian Dawkins
Michigan Tech
Engine Group

[MikeWaggoner at UW]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Travis:
It is after all a pretty short event...and the motors aren't exactly making tons of power...

Travis<HR></BLOCKQUOTE>

The engines aren't operating at RPM's where power production is the most signifigant stress, it's the RPM... What school do you go to and not know this? /infopop/emoticons/icon_confused.gif

Western Washington University FSAE
dot.etec.wwu.edu/fsae

[Travis Garrison]

Thank you, a stupid mistake on my part. My overall point still stands, aluminum rods could very probably still be made to work, provided they were replaced on a regular bassis. As was pointed out there are other things that should probably come off first if a team is interested in reducing rotational inertia...and overall the rods shouldn't be very high up on the list of most teams. I was simply trying to point out it is a possability, it was done on our V8, and it worked...

As for the forged Ti blanks...I don't see why that would have to be the case...but then I haven't done any calculations...however I find it unlikely that the difference in strength would be such that Ti rods would no longer be an option...I think, like the tooling wear the point is being exagerated slightly...

That being said we have no intention of puting different rods on our engine, just not time effective...very small gain for alot of work. I think that if a team were operating with a large budget, either in terms of man-hours or money it might be worth it, esp since it doesn't show up on the cost report ("free" as far as the competition is concerned)...but not for us, since we have neither an excess of man hours or money.

[Spike]

The U of R has two full time machinists. One of them is an ex-Tool&Die maker. They do the bulk of the machining for the car. I guess we are just lucky to have professional machinists doing our work. As I'm sure you know, James, what damage a broken rod can do. Unless you have a couple of spare engines laying around, making your own aluminium or Ti rods might be a costly endeavour. Because when the rod fails it will destroy the engine. As for the custom vs. stock cost,, I think if you ever have too replace all four you will have other things to worry about besides making your own rods. A fellow racer put a rod through the block of his GSX-R 750 at 210km/hr and 13,000. It split the block, the oil pan, and ended up logging itself in the transmission. But good luck to you if you decide to make your own. As for removing the charging system you're right, you will learn nothing. But if you are looking for a cheap, simple gain it is the way to go. And if you want a design challenge make a lighter rotor and stator.

[Michael Jones]

...besides, there are plenty of conrod manufacturers out there, doing forged Al and Ti rods. Saw at least 15 at the PRI show last week, although not for bike engines of course.

That noted, any modifications cost $$$ that most teams (including ours) don't have.

Making your own is cost-effective if you assume labor is near infinite and free, which is essentially the economics of FSAE, right?

[drivetrainUW-Platt]

Hey, i know this is a very old post, but i just thoughts since i have gone thru all the newer ones i should start from the beginning and check out what was goin on then....anyways, what is meant buy you will not learn anything from removing the alternator???

[Chris Davin]

I have several remarks on the topic:

-First of all, "drilling out" connecting rods seems like a very bad idea. You need to realize that the rods were designed with very tight safety factors to begin with. Sure, maybe they see slightly different operating conditions in an FSAE engine, but drilling holes through them creates big stress concentrations and will almost certainly cause them to fail.

-Making custom rods out of titanium is an idea that has more merit. Titanium stock and carbide cutters are both quite expensive, but (as was pointed out previously) so are replacement stock rods. It would be an interesting design project.

-Do not expect to see anywhere close to "MASSIVE horsepower gains." Steady-state the motor should make exactly the same amount of power as with steel rods. Gains are only realized when the engine is revving up. Admittedly, this is pretty much always the case on the race track, but the inertia of the conrods is pretty small when compared to that of the entire car. The improvement in acceleration can actually be calculated quite easily.

-Clearly, a team cannot possibly pursue every project that offers to improve the car. Ideas should be pursued in some kind of logical order, considering the benefits, costs, and risks. For this project, the benefits seem small, the costs high, and the risks great. (Throwing a rod will at least destroy an engine, and should it happen during the endurance event, disqualify you.)

[Ben Beacock]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Chris Davin:

-Do not expect to see anywhere close to "MASSIVE horsepower gains." Steady-state the motor should make exactly the same amount of power as with steel rods. Gains are only realized when the engine is revving up. Admittedly, this is pretty much always the case on the race track, but the inertia of the conrods is pretty small when compared to that of the entire car. The improvement in acceleration can actually be calculated quite easily.
<HR></BLOCKQUOTE>

Connecting rods are never steady state unless you can make torque at 0 rpm. They are constantly changing direction and receive a helluva lot of acceleration (especially at 12-13K). It is mainly linear acceleration but there is also a small rotational acceleration. Of course, this applies to the piston as well (but not the rotational part)

[gug]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Ben Beacock:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Chris Davin:

-Do not expect to see anywhere close to "MASSIVE horsepower gains." Steady-state the motor should make exactly the same amount of power as with steel rods. Gains are only realized when the engine is revving up. Admittedly, this is pretty much always the case on the race track, but the inertia of the conrods is pretty small when compared to that of the entire car. The improvement in acceleration can actually be calculated quite easily.
<HR></BLOCKQUOTE>

Connecting rods are never steady state unless you can make torque at 0 rpm. They are constantly changing direction and receive a helluva lot of acceleration (especially at 12-13K). It is mainly linear acceleration but there is also a small rotational acceleration. Of course, this applies to the piston as well (but not the rotational part) <HR></BLOCKQUOTE>

i dont know much about engines, but how much of a factor is friction between the con-rod and the crankshaft? i can see how lighter con-rods would reduce this and generate some power gains, but i have no idea how much gain.

anyway, im all for reducing rotational inertia in the engine, nothing sounds better than a quick revving engine. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

btw Mike, the "you will not learn anything from removing the alternator" comment was about it being a simple task that doesnt require you to learn anything new. drilling holes in your con-rods will certainly teach you something, although it might only be how much damage it can cause...

[Ben Beacock]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by gug:

i dont know much about engines, but how much of a factor is friction between the con-rod and the crankshaft? i can see how lighter con-rods would reduce this and generate some power gains, but i have no idea how much gain.
<HR></BLOCKQUOTE>

I don't know for sure, but I would assume the majority of the friction comes during the power stroke, which is probably orders of magnitude higher than the inertial forces of the rod/piston. I suppose it would also get alot of friction during the intake stroke when the throttle is suddenly closed at high rpm (which is maybe why they blow up at that point?)

I had a Porsche engine engineer discuss crankcase ventilation when we were displaying the car at an autoshow. Aparently a partial vacuum in the engine cuts down on the air drag of the crank/rods as they spin. minimal gains, but they all add up eventually.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
anyway, im all for reducing rotational inertia in the engine, nothing sounds better than a quick revving engine. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
<HR></BLOCKQUOTE>

Me too.. i'm trying to do that with my VW Scirocco engine. (destroked 2.0L, lightened flywheel, light crank pulley, knife edged crank, ect). Seriously looking at the rods and pistons now.

[Chris Davin]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Ben Beacock:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Chris Davin:

-Do not expect to see anywhere close to "MASSIVE horsepower gains." Steady-state the motor should make exactly the same amount of power as with steel rods. Gains are only realized when the engine is revving up. Admittedly, this is pretty much always the case on the race track, but the inertia of the conrods is pretty small when compared to that of the entire car. The improvement in acceleration can actually be calculated quite easily.
<HR></BLOCKQUOTE>

Connecting rods are never steady state unless you can make torque at 0 rpm. They are constantly changing direction and receive a helluva lot of acceleration (especially at 12-13K). It is mainly linear acceleration but there is also a small rotational acceleration. Of course, this applies to the piston as well (but not the rotational part) <HR></BLOCKQUOTE>

You are right that connecting rods are always accelerating as long as the engine is turning, but they do not soak up power unless the engine is revving up (ie dN/dt&gt;0). The effect of having light rods would be the same as having a light flywheel - the enigine will rev faster in neutral, and the engine will also deliver slightly more power when it's revving up, but if it's being held at a constant RPM, power will be the same.

I think the difference in friction between steel and titanium rods would be very small, probably negligible. If the clearence in the rod bearing is the same, and the speed of the engine is the same, the shear in the oil should be the same -&gt; same frictional loss. Without doing the math, there might be lower normal forces between the piston and the cylinder wall, but I'm not sure.

The biggest reason people invest in titanium rods is to get more R's from their motor. In a non-restricted engine, more R's = more air = more fuel = more power. However, since our engines are intake-restricted, the benefits of titanium rods seem to me pretty small.

[gug]

hey Chris, does that mean you think friction between con-rod and crankshaft is negligable too?

[Dr Claw]

Well, if all else fails, you can factor in the coolness factor.

http://ltufsae.nx-tech.com/gallery/albums/2004/100_2526.sized.jpg

i mean, seriously, which is cooler? All you'd need is a clear acrylic block so that the judges could see the titanium rods, and you'd win design...or something.

Though, how often are you at a constant RPM?

[Ben Beacock]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>
You are right that connecting rods are always accelerating as long as the engine is turning, but they do not soak up power unless the engine is revving up (ie dN/dt&gt;0).
<HR></BLOCKQUOTE>

I suppose the reason is that the rod/piston linear motion is reciprocal. For a 1/4 turn you are accelerating it (energy in) and then the next 1/4 decelerating it (energy out) which would (neglecting friction and rotational losses) cancel each other out.

[Travis Garrison]

Ben,

That Porsche engineer might have had pumping losses on the brain. I'm pretty sure the boxer engines have been plagued by massive pumping losses in the past, so the returns for a Porsche getting the air out of its crank case would probably be much greater than what we would see if we ran a slight vacuum in our crank cases.

I'm not saying there wouldn't be gains, I don't know, maybe someone has hard data comparing HP w and w/out dry sump setups on a 600.

...Just playing devils advocate here and pointing out that the source may have been a little biased towards that particular approach.

Travis Garrison

[MikeWaggoner at UW]

There was an article in hotrod magazine that showed 35 hp gains on a 381 SBC with high vacuum. Hayabusa.org had a lot of discussion on this, and saw 2-3-4 hp dyno gains from low vacuum. I'd think since we have almost infinite vacuum thanks to the restrictor, similar mods might not be a bad idea to try.

[Charlie]

Yes I have that Hot Rod magazine and it has led to a lot of misled people. That engine had special low-tension rings that were designed for a crankcase under vacuum. And they were pulling a ton of vacuum on that engine too.

There are benefits but that article seems to have burned its way into everyone's brain. And its a 400 HP engine too, so that's less than a 10% power gain. Not bd, but when its designed for the vacuum as it was its a different story.

[Chris Davin]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by gug:
hey Chris, does that mean you think friction between con-rod and crankshaft is negligable too? <HR></BLOCKQUOTE>

Two things, to clarify:

1) Thinking a little more about it, if you change to titanium rods but leave your rod bearing clearances the same, I think the frictional losses in said rod bearings should be the same. The rod bearings will certainly be supporting less load with lighter rods, but I think the frictional losses are related to the shear stress in the oil, not the supported load. I will, however, make no claims about the frictional loss between the piston and cylinder wall.

2) I calculated the power loss in the hydrodynamic bearings of our engine once, and I think it came out pretty small, a few tenths of a horsepower, if I remember correctly. It's up to you whether you consider this negligible.

Cheers.