Kevin

Brad you're spot on... I didn't sell them to K24madness, and I didn't sell them to you and others with stock engines.. I don't need to take the money when I know the results.. Life is to short. I applaud K24madness for doing this, it takes *****.

hatchy

K24madness, looks like there is a little more lag with the bigger wheel.. Does it change the way you drive the car?

Jean

K24

Congratulations, you will have one very fast car. You have put a lot of effort and research behind it going back through your posts on the forum.

I think the first thing to consider is what is the real torque you are getting with this setup and how you manage the heat, you first need to do some runs on a different dyno I believe. I am very far from being an expert at all but I hear there are better ones (as in more accurate and less prone to sensitivity to parameters) I also hear the Andial I/C is very good and if you run safe AFRs you should not have an issue as long as you stay within the 1 Bar arena. I am sure Todd K. must have told you that.

I said it in another thread before, 90% of the tuners in the US and Europe will tell you that you should be fine with your stock rods up to 600hp (torque) if they know you are not ready to open the case and just want some bolt-ons. It would be stupid to loose the sale when the engine can last decently in some cases and last for very long in others if you are lucky. They will recommend against it though.

As Kevin said, tell them you are willing to open the case and see which way they lead you.

Not a single European tuner (decent ones ala RS, Manthey, FVD, Cargraphic, Sportec, etc..) will sell kits in bulk that take you beyond 550hp, why? Not because they can't, but because they can't reliably. They would have to shut down their businesses after a few customers come back with broken engines. Not worth the gamble. You want more? Sign a disclaimer.

Stress on your engine almost doubles between 1 Bar and 1.2 Bar, I would run it for very short bursts only. This does not mean that your engine will fail soon, and I have seen some stock ones taking real boost abuse and still running, but you will be playing with fire.

Now time to post some 60-130s. Enjoy the car and post some pictures! Congratulations.

TB993tt

Sensible discussion going on here. Just to give my perspective to Kevin's comments on the new K24/26 platform, RS use their race version of this unit on their Ring record 996tt which puts out up to 700hp. I have the same (or very similar, different housings for 993tt and internal wastegates) units which "only" run 540hp on the engine dyno. The limit of my maximum power is not the turbos or rods or flame rings or lack of twin plugs or cams or exhaust back pressure, it is heat. RS know at what levels these motors will start breaking and need race motor type maintenance programs and they can program the Motronic to keep the engine (most importantly boost levels) within their levels which can mean a lot more than 540hp under certain conditions but less under others. This is my ongoing worry for those who rely on a basic map and manual boost control. Once you are at the outer limits of the heat parameters of the motor, what is going to happen ? If you continue running 1.2bar under those circumstances it will not be pretty. Getting back to Kevin's apprehension, imagine a set of these K24/26s on a manual boost control motor which is fairly stock, when the owner wants to try winding his boost up a bit - 1.2 bar @ 6000rpm with these puppies will be giving you 700hp "worth" of hot air - but what will you stockish motor do with it $$$$$$
Madness
Your set up looks like good value for money and will doubtlessly be fast. I have to wonder what is happening in your motor at say 4500-5000rpm where a twin plug, cammed Motronic boost motor will be turning your 1.2bar into around 520lb/ft (which IS close to rod bending territory) . But I do not wish to knock (the engine can do that for itself ) your set up. Thanks for sharing the information

Geoffrey

I completely agree with Kevin on the 550hp number. I won't tune a car with stock rod bolts (or rods in the case of a 993tt) beyond 550hp, which is one reason Tal's car was limited to .7bar of boost. I have run a 930 rod with ARP rod bolts to 521hp AND 7800rpm with no issues, however that is a much stronger rod than the 993tt and has upgraded rod bolts.

Remember that these engines have very short rod to stroke ratios and put a high level of side loading on the rod itself. This in turn puts significant stress on the rod bolts which in stock form are rather weak.

Woodster

BRAVO, BRAVO, K24 I love this stuff.
I understand your turbos are modified ($600) k-24, but I did not understand what the
other turbos are??
I have kevin's K-16 hybrid, stage 2, zero clearance, ceramic coated impellors: how would
they compare? I have not found 4-wheel dyno in Minnesota yet but at .9 bar and
92 octane "this mother flies!!!!!!!!!!!!"

K24madness

Rods experance two different type of loads. One is compressive from (torque). This is what bends rods. That being said my car produces very little additional torque from the stock K24 setup at 1.1bar. XXX torque at whatever RPM still excerts the same compressive force on the rods. Cylinder pressure regardless of where it happens in the RPM band is the thing to be concerned with. I have limited that.

I disagree with you Kevin on there being different load allowances between the 996 & 993. These rods are the same part number from Porsche. While the water cooled motor does benifit from a more stable piston/bore relationship due to controlled temps surrounding the bore the rods do not. Both cars have the rods cooled by oil.

Lastly the other forces on the rod deal with the bolts and end caps. Even if the motor produced stock torque they would fail from over spinning the motor. The crankshaft trying to pull the piston back down after the exhaust stroke is where the largest forces occur in this area.
(During the compression stroke the piston has opposing forces that help push the piston back down thats why its only the exhaust stroke that matters)

Rest assured I am no rookie when it comes to dealing with motors. I have built some monsters over the years. I am also a big boy when it comes to dealing with the consiquences of my actions. This car is a blast to drive. A collection of well thought out parts. Once I finish fine tuning the fueling I will drive the wheels off of it.

I am also supprised that nobody has mentioned detonation. The destructive forces from detonation on a rod are well documented. This is why I only run 103oct. Destructive Rod forces multiply 2-4 times when this occurs.

"They also mocked Columbus when he left to discover the new world"

K24madness

On another note Viper Bob has been running his car with stock internals for 5,000 miles with lots of track time at up to 1.4 bar of boost.

More food for thought.

I hate to play keyboard tuner but there you go.

Jean

K24

I will not get in the way between you and Kevin. But Kevin is a bit more than a behind the keyboard tuner, and I want to make sure he stays here with us

I am not an experienced engine builder nor an engineer nor have ever had many high hp cars, but I have spent a lot of time talking to knowledgeable people and putting their information in conflict with each others'.

I have seen pictures of bent and broken rods from the US to Europe, while trying to convince myself that I did not need to open my case, and that these guys only wanted my money. Funny enough, the good ones (reputable rather, in the racing world) did not accept to take the job unless I opened the case and I was talking 600 hp at the time, others did not accept to give me a 600 hp engine unless they had the whole car.

If there is one thing both builders in the US and Europe agree upon, is that the rods of the 993TT will not live reliably beyond these hp/torque levels. The rod bolts fail, the rods bend. I am not sure why you say that youyr torque did not increase much when hp is a function of torque

You raise excellent and accurate points, however you are not 100% correct, as rods DO get more stress and bend due to higher RPMs and not only because of compressive torque. We do not mention detonation because most of us have Motronic, not aftermarket EFI and we are somewhat protected against it through the knock sensors. So we do not really worry about it as much as we hsould.

The only reason the GT3 has titanium rods and rod bolts is because the steel rods of the 996 were designed to be used at 6750 RPMs reliably and will brake at 9000 RPMs. Weight savings was a bonus. It is not the torque, it is the RPMs and the stress they cause on the rods and bolts

Engine and head temperatures also play a major role on steel rods and any other material, one of the reasons why the 996 engine is more durable at higher hp levels. Kevin can certainly give you many other better explanations.

The example of VB has no real value, 5000 miles? I hope this is not the longevity you are targeting. We are talking engines that will have a life not much shorter than stock (20-25%), otherwise this debate is worthless.

As JJayB said in the other thread, It is all about how much do you drive your car under the extreme conditions, the rods will not just bend because your engine has potential to go beyond 600 hp! Do the 5k miles at those levels and they will.

Finally, we are not discovering anything here, remember anything and everything has already been done on these engines over the last 10 years or so, rods or not, 800-1000hp for 2 seconds, turbos, exhausts, EFIs, you name it. It is only what each one of us will discover on his own, but literature is there.

As you said, it is your choice, we are just trying to help.
Please post some acceleration numbers whenever you can
Best

K24madness

Jean I respect your Adult response to my threads even if you disagree.

#1 I have only increased maximum torque by 14 ftlbs over the standard K24 setup. The fact that I was able to carry the peak torque over a broad portion of the RPM range is were I achived the HP increase.
Remember torque is the "force" on the rods. HP is only a fuction of torque X RPM. The loads are not collected and stored. Regardless of how many times per minute you apply that "torque" the sum will not change.
I agree there is a limit to the torque that can safely be applied to the rod before they fail (bend) from these forces. I have stayed well within them.

#2+3 I agree 100% that RPMS do "break" rod bolts and end caps. Not bend. They bend from peak torque forces. I have stated that in my previous thread. You need to limit the PRM's to be safe. I like to keep it below 6,200 RPM

#4 The events that take place above and below the piston are two entirely different things. While I agree with Geoffrey that CHT's & EGT's will limit safe power output I disagree that by increasing HP as a fuction of carrying the same torque output further out the RPM range is unsafe.
Rods do not care if there is a water jacket around the piston or not.

hatchy

I know you guys are just trying to help K24madness out by giving him "common rennlist wisdom." K24madness is clearly not a newbie and knows what he is doing, and I think it is cool that he is willing to explore the limits a little.

Rassel

Another interesting and educating thread. I'm putting rate on this one, so everyone can see it has some quality questions and answers in it.

TB993TT has a good point in the heat issue.
I was recently looking at a 993GT2 EVO, stripped from the M64 engine (without from factory) to see if we could put another engine in there, due to the extensive heat the M64 generates over long time. Previous owner used the same solution. I want to however flag, that this doesn't mean that the problem can not be solved, just that we chose a different path.

Kevin

Well I did get another reassuring opinion from Gunter these last few days. I guess that in all fairness we can all agree to disagree. One has to make the decision as to there own safety values and limits that they want to have on there own engine.

Rassel

It's getting way to simplifed here. When pushed to the limit a rod can be killed by plenty of reasons. Torque, unbalance, frictional forces, internal stretch, uneven crystalization in the material etc etc..

K24madness

This thread has gotten spun around quite bit.

The thread started with intention of educating people as to the results of different types of compressor wheels installed into the same housing without any other mods. I was also showing how the K24 compressor does not flow enough air for a 3.6ltr motor at 1.1 bar. I proved my research with the above dyno chart.

Kevin I do respect your knowledge. You have had lots of time under your belt with the 911 style motor. The issue of reliabilty that you brought up was the rods. I have a strong case for why you are wrong there. I do agree that I am pushing the limits of the motor. I feel that the real risk is the heads lifting due to high CHT and cylinder pressures. This type of failure does not concern me. If and when it does occur I will drop the motor and address it as well as some other things I plan to do in the future.

I can understand why you would like to steer most folks well under the safe limits of the motor. If you tried to coax them into making more power that you felt was safe then you would be unresponsable.

We can agree to disagree.

I think you would agree that the results of my actions will be educational for all.