If the compression is the only thing that has changed ( no cams, etc.) then the tune should be close. The lower compresion will give a richer and dirtier burn because the car will have been tuned a little richer anyhow to keep detonation down with the stock higher compression. The lower compression will just magnify the richness of the tune. Like Phunk said...if you add the AAM system at the same time then you are changing a fuel delivery variable that will change the fuel amount being put into the motor. So why do it right away?? Like you said...you have this amount of money in the car now....why take the chance and have to do the motor again.

 

You may have forged internals but a bad tune can kill rings too. A broken piston or rod means that an engine would have to come apart again...just like rings that did not properly seat from too much fuel during the break-in. I have seen friends with 500 mile motors that were running too much fuel from a bad tune and the rings were ruined because of too much fuel washing the cylinder bores of oil. They pull the motor apart because it is smoking on deceleration and under power and the ring edges are so sharp you could cut paper with them.

 

I am in the process of arrangin a mild engine build up: forged pistons, rods, valves and valve springs. If I use a "turbo compression" set on an NA motor to break it in before I get the twin turbo (APS) is that bad?

 

I don't think it would be an issue...I considered it myself. The only problem is that unless you are installing a supercharger or single turbo it is almost easier to have the motor out of the car to install a TT kit. Some say why do it twice??

 

I currently have my LB in the shop with similarly discussed mods and intend to add the APS system. In order to keep my engine builder "honest" I have been considering this one-two approach, even though hours can be saved with the all in one build "big bang approach. Since the APS TT for G plumbing is not out til ~March and my LB will be done in Jan, I am still considering this two step approach.

Oh yeah if you are doing valve springs and rods , you prolley wnat to consder at leas ta mild CAM upgrade. I am using the JWT S1.

 

Gents, this has been a really good read. Todd and I are basically in the same boat with only a few weeks in between. In fact, we are even using the same shop, Greddy TT, and future set up as well. Here's my question, what about installing the AAM fuel return system and waiting to change out the injectors until after the break in period? I know that the AAM system will deliver fuel in a much better way than before, but would that cause you be rich enough to damage rings? how about, installing the AAM system and checking the tune? If all is well, then swap out the injectors after a couple of weeks?

 

ernie:
i asked the same question on another thread..let's see if we get the same response!

 

With the new fuel system, you will likely be running a bit rich at the top of the RPM range. From idle to 4000rpm, I doubt you would tell the difference. You'll use the eManage to scale the larger 550cc injectors that we all bought, and can fine tune from there. I certainly would hire someone to tune your cars right away...once you decide on you will break it in.

Remember, that everyone will have a slightly different method of breaking in a motor. None of which is decidely better than the other. Just trust your machine shop, and the piston manufacturer, to guide you in the break-in process.

 

It looks like this issue has been covered pretty well, but I thought I would add a bit to help some people understand what is happening when you break in a new motor. This is a pretty controversial subject among tuners, and I've seen this subject cause some ridiculous arguments...

First off, let me say that my method of breaking in a motor includes running the car at WOT in top gear within MINUTES of getting it warmed up. If that scares you, read this.

http://www.mototuneusa.com/break_in_secrets.htm

 

That well worn link (although I couldnt open it) has made the rounds of just about every motorcyle, car, and lawnmower racing website. It seem very authoritative..but it is still very controversial...and anything but conclusive. Too each his own....good luck!

 

I agree that it is controversial, and not conclusive, but I don't think anything on this subject will ever be conclusive. In the end all we can do is go by who or what we believe, and see what happens. His method has never caused me a problem, but the races that I have won after breaking in a motor like that could very easily be attributed to driving skill instead of the engine making more power due to the break in process...

 

This guy claims that the manufacturers are wrong because they say to baby a brand new engine. Some manufacturers already break the engine in for you but most of the time they give you instructions to break it in easily but the instructions are not for the engine-they're for the rest of the car.

On a new car you have not only a fresh engine but also a new clutch, flywheel, pressure plate, you also have new discs and brake pads etc. If you took his breakin method then you'd have a wonderfully broken in engine and a clutch that's only going to last 1/2 as long. Same deal with the brakes.

 

i will revive another buried thread...since this should be my reality tomorrow!!! i'm not gonna sleep tonight...then again, i shouldn't get too excited until i am actually driving my car away! (supposed to take delivery of my car tomorrow and dyno on sat)

 

Alright now you know that we expect a review sometime today! Congrats, btw. It's been a long time coming for you... Like a kid on Christmas Eve.

 

Yeah, I know. Now I've got to get my **** built now....