Porting, Polishing, and Cams project
I'm sure the added power puts more strain on the motor and reduces its lifespan to some degree. I was at the Dyno shop awhile back and was waiting in the lobby area talking with a guy who just brought a new STI in for $10K in mod work. Another guy asked him how long he thought this motor would last and he replied with "45,000". I kept quiet and continued to listen, only to hear him say that his last STI only lasted to 50,000 before the motor blew. Granted, these are 4cyl cars with more power / boost than our car, and can only take so much before giving out.
If my car lasts to 145K, I think it will be a miracle.
And unfortunately its all in the cost/performance analysis. I'm also sure that considerations that we are not aware of (as Jerry was explaining) are a factors too. In general though, the valve upgrades are more expensive and take longer to make. If you have a blank that is turned on a CNC lathe, as soon as you are done there it may go to finishing, but then it's done. The swirl-polishing is an extra step and the back cutting is too. Specialty tooling and more time = more costs.
But on the same theory you are asking about, why don't the manufacturer's have better flowing exhaust from the Factory? Why don't they port the heads / intakes / ect from the factory? Why don't they use as much carbon fiber as they should? It's all about the $$ on the bottom line. Not to mention that them not doing so provides me a job
For longevity, it really depends on the mods and how it's tuned. I mean you can have a stock engine with a bad tune and blow it up because it ran too lean for too long. Portwork in general only refines what is there and shouldn't have adverse effects on longevity as you are making the combustion process easier on your engine. For a rule of thumb though, most have taken the approach that 10-20% more power can be had without adversely effecting longevity too much. Again this is a generally accepted theory and doesn't apply in all cases.
But on the same theory you are asking about, why don't the manufacturer's have better flowing exhaust from the Factory? Why don't they port the heads / intakes / ect from the factory? Why don't they use as much carbon fiber as they should? It's all about the $$ on the bottom line. Not to mention that them not doing so provides me a job
For longevity, it really depends on the mods and how it's tuned.....Portwork in general only refines what is there and shouldn't have adverse effects on longevity as you are making the combustion process easier on your engine. For a rule of thumb though, most have taken the approach that 10-20% more power can be had without adversely effecting longevity too much. Again this is a generally accepted theory and doesn't apply in all cases.
I believe companies don't do all these modifications mainly because of cost.
Secondly, these mods will cause the car to have a rougher idle and could effect emissions to some degree. If the car didn't idle smooth or had any other "side effects", some drivers would think something is wrong with the car and bring it in.
Last but not least is the fact that the trq and hp numbers won't be so close together. MB might have wanted to car to have a smooth powerband and chose the setup they did because of this. The guy that did the heads said they were some of the best stock heads he had seen and it had a great valve job from the factory.
It could have been as simple as MB wanting a car to compete with the M3.
It's a good question and I would like to hear other opinions...
By the way, Jerry I can't focus on anything at work... Just keep thinking about the ECU arriving tomorrow...
Plus you can look at it this way, sure these engines are hand assembled, however they are still mass produced—granted not in huge quantities like GM or Toyota. Sure we'd like to think that no cost was spared on our cars and that all the components are the best out there but that isn't the case with any car. More power can be had to any car out there. Cost alone is the answer simply because hours can & are spent porting heads alone. To get every head for every car to flow the same would be a monumental task to say the least.
You can look at CNC'd heads too for example, but again cost is the factor. One look in a Brodix head catalog for a good flowing "as cast" head is considerably less than a CNC'd version.
If auto manufacturers did get all the horsepower out of these engine then it would be a boring aftermarket (if any).
My engine idles nicely at about 500rpm, even after driving 5000+ miles with the cams and headwork. No problems at all, except for a faulty coolant level sensor that I need to change. The ECU and TCU adapted after a few hundred miles of driving. The motor ran great from the beginning, and it's running better now after the adaptation.
as far as i know my cams are still on order- i'll check with the vendor tomorrow.
My engine idles nicely at about 500rpm, even after driving 5000+ miles with the cams and headwork. No problems at all, except for a faulty coolant level sensor that I need to change. The ECU and TCU adapted after a few hundred miles of driving. The motor ran great from the beginning, and it's running better now after the adaptation.
The Best of Mercedes & AMG
The idle isn't so easy to change and it is a sub-routine within the ECU. Renntech did say that the cams are drastically different than the original specs I sent them.
Pshek - do you have the specs on your cams? I would be willing to bet they are the ones for the N/A motor.
Look at the exhaust side. Oversized exhaust ports are as detrimental as oversized exhaust tubing. A low pressure zone in the exhaust tract will kill velocity, which results in a loss of inertia. No inertial equals no scavenging, which dilutes the combustion chamber with excess exhaust gases. Cam lift, duration, combustion chamber design, maximum RPM, the RPM for proposed peak HP, intake, exhaust, cylinder capacity, and stroke all play a part in determining the optimum port size. Bigger isn't always better.
The ECU cam back from Renntech and it helped a little, but the car is still misfiring one Cylinder 1 when at idle. Cylinder 1 also has a low 60 PSI compression with the Schrick cams installed. Note: The car runs GREAT with the AMG cams and has no issues.
MB thinks that it is the cam and recommends that I put the AMG cams back in. They think that the cam is keeping the valve from making a good seal.
I have sent an email to Schrick asking them to call me in the AM to see about getting another cam sent via overnight delivery. If they can't do this, them I'm going to ask MB to put the AMG cams back in and take the car as is. I will then either wait on replacement cams and install them on a later date, or abort the project all together and stick with the ported heads.
I have now incurred another 5 hours labor with MB that wasn't planned for.
Your suggestions / feedback is welcome.
If, in fact, one of the valves is failing (either intake or exhaust) in #1 cylinder to seat, the culprit may be a faulty hydralic valve adjuster. Because aftermarket cams are frequently ground with a different dimension base circle, it could be that the lifter (hydraulic roller follower) has run out of its adjustment range and it bottomed out. If that were to occur, it would hold the valve off the seat when it should be closed. That would drastically reduce compression and lead to a dead cylinder.
Last edited by splinter; Apr 25, 2007 at 08:25 PM.
If, in fact, one of the valves is failing (either intake or exhaust) in #1 cylinder to seat, the culprit may be a faulty hydralic valve adjuster. Because aftermarket cams are frequently ground with a different dimension base circle, it could be that the lifter (hydraulic roller follower) has run out of its adjustment range and it bottomed out. If that were to occur, it would hold the valve off the seat when it should be closed. That would drastically reduce compression and lead to a dead cylinder.
If you could be so kind as to provide a list of things for MB to check, I will get with them to see what they have done.
Wouldn't the other lifters be performing the same as well if that was the issue?
With the cam still in the car you could ask tech to measure lobes on #1 and on any other cylinder and compare measurements. If cam lobes are the problem it will be obvious.
Call me with any questions.
949.584.4446.
Have you considered returning the schrick cams and getting Kleemann cams??? Which are supposedly straight drop-ins (assuming things don't work out with the schrick cams of course).
Last edited by MB_Forever; Apr 25, 2007 at 09:28 PM.
Vadim - I'll ask MB to check what you mentioned and I'll personally call you with the results. Would you mind talking with MB directly? I'll be more than happy to pay you for your time.
I really don't want to abandon the project, I just hope it comes to an end soon.
you are like our lab-mice for new mods
They requested that I have MB do a compression check on the other cylinders and if they test fine, then I'm to return the cams to Schrick for measuring / approval on replacement. They did mention that they are proud of their product and would take care of me in regards to the extra labor I have incurred.
The only issue I can forsee is if the Schrick cams measure fine when they get returned.
Thoughts?
The good news is that I'll get the car back with the AMG cams... which means I get to hit the Dyno so we can see what the porting / valve job did in the power department. It will be up to two weeks before I will get the replacement cams.
They requested that I have MB do a compression check on the other cylinders and if they test fine, then I'm to return the cams to Schrick for measuring / approval on replacement. They did mention that they are proud of their product and would take care of me in regards to the extra labor I have incurred.
The only issue I can forsee is if the Schrick cams measure fine when they get returned.
Thoughts?
The good news is that I'll get the car back with the AMG cams... which means I get to hit the Dyno so we can see what the porting / valve job did in the power department. It will be up to two weeks before I will get the replacement cams.
get the cams measured before you send them back...this way you have some evidence in case they try to blame something else...







