This is somthing that I have been thinking about for a while and guess that it could be a pretty big project to get an old engine to have the same power it did when it was brand new. I am guessing worn gaskets, lost compression, carbon build up to be some of the more prominent answers.

So what causes an engine to lose power and how would you get an old VQ (4th gen with let's say 150,000 miles that has a solid block and has been regularly maintained)to run like new (as far as power?) Would you do a carbon flush, clean out the intake manifold, clean the exhaust manifold, and replace gaskets and seals? Or do you think it would take a more detailed job like new pistons, pistons rings, rod bearings, main bearings, gaskets & seals, camshaft, and resurface all cylinder heads and machine all valves & seats?

I was just wondering how well these VQ's are built and what it would take to restore power from an old engine to like new.

 

150,000 miles is not a lot for a modern engine. As long as the compression is good and nothing is clogged up in the intake or exhaust tracts, it should be good to go.

 

Let's say just for arguments sake that you are modding your car like Neal, yet your dyno's are not improving the way you want and you attribute this to an old engine. How does an old engine cause you to lose power?

 

An old engine won't respond to mods well if the compression is bad. Bad compression is a trait of older engines. Usually wear and miles make the rings wear and that causes a loss in compression. You think you have bad compression? Do a compression and leakdown test to verify. It's really the only good way to know.

 

Well, with low-mile used VQs out there for less than $800, it's not worth doing a ring job if you have bad compression.

It would be cheaper and easier to just put in a new engine.

 

My car is running great and according to the cars that I have beaten is running really strong. I was wondering if I should be concerned with things like build up in the intake manifold, carbon build up in the engine, and what kinds of things I could do in the future to keep the car running strong besides just regular maintenance.

Thanks for all the reply's, I may just get a compression test just to see. Would there be anything else besides poor compression that could lead to power loss. Is carbon build up or clogged injectors very common on an old engine, what would you do about this?

 

You can get rid of the carbon build up on the pistons/intake manifold. http://www.importracer.net/articles/carbondeposits.html

This is a simple article I've found. Miata net has a better write up. I used the Seafoam spray cleaner to do this but alot of stuff will work. Remember to change the oil right after.

 

THANKS!!

 

I wouldn't worry too much about a VQ loosing power and I sure wouldn't use Neal's dyno as a reason to worry. Neal's car was dynoed on a dyno that makes very low power readings. The same day Neal's car was there a M-coupe made 210rwhp and a chipped Audi TT made 164fwhp. These numbers are about 15-20whp lower than I've seen on my own dyno and just about everywhere I've read on the net.

Have you seen the pics of EJJ's VQ teardown? His motor had 87K miles and had used nitrous and boosted for 4k miles yet the cross-hatch marks were still in the bores!!!! That's amazing. Due to the design of bore and crank, the VQ has a very low piston speed which is great for reliability. Pretty much everything about this motor is bulletproof from an NA standpoint. How many posts have you read where someone who's always ran NA reported any sort of low compression? There are plenty of Max owners out there pulling awesome track numbers on high mileage motors.


Dave