Engine building question

Cruisin04Neon · Post by **Cruisin04Neon** » Tue Apr 17, 2007 10:59 pm

Hey Crew.

I was thinking about building a motor wheather it be a DOHC 2.0 or SOHC or 2.4 ect. For now lets go SOHC.

I was curious what benifits you might gain by boring your motor .20 over? Would just doing that and changing the pistons be worth anything?

I was also thinking about a header. I was looking at the OBX with the downpipe. Now does that pipe have provisions for the O2 sensors?. What would i have to do to get it to work?.
I run a Flowmaster 80 and i like loud. Its loud already its only 2.5 out so nothing fancy.

Im just trying to get a little more umph outta my car.

Last of all. Turbo kits. If i where to get one, is there issues with setting it up due to the NGC?. its probably run stock boost 5-8 until i built a motor.

Thanks

OB · Post by OB » Tue Apr 17, 2007 11:46 pm

To answer your first question, boring the cylinders is an effective way to increase compression, as well as a slight increase in displacement. Both of these translate to increased power and torque. The exact numbers depend on a lot of things, such as the pistons used, and the tuning parameters. Higher compression will net good power gains, but require some fuel/spark tuning and higher octane gas. The larger displacement typically translates to solid torque gains, but will also need some tuning consideration for maximum reliability and effectiveness.

Not too sure about the OBX header/downpipe combo. You might wanna check out their site or a dealer and ask them about the specs. Any quality manufacturer will usually include 02 bungs in their short tube headers, while the long tube versions are generally for 'offroad use only' and require you to make your own 02 accomodations. All of this can be arranged by a good exhaust shop, and like just about anything else, you'll want to make arrangements for tuning (a wideband 02S setup, for example), especially if you delete the cat.

As far as turbo goes, you will definatly have to come up with a way to get around the stock PCM, ngc or not. A standalone ems, such as a megasquirt setup or equivalent, will solve this issue.

Bottom line, to make any power in the sohc motor, tuning of the computer is required. Bolt ons will make a few ponies here and there, but a real NA or forced induction build requires lots of tuning, and lots of money.

03blackrt · Post by **03blackrt** » Wed Apr 18, 2007 12:23 am

I hope you mean 0.020", because 0.20" is a HUGE overbore. And boreing it not very effective at increasing displacment. Increasing stroke is the most effective.

OB · Post by OB » Wed Apr 18, 2007 2:10 am

^Yeah I guess the way I put it kinda made it sound like it was gonna be a large increase. Fixed!

jckevns · Post by **jckevns** » Wed Apr 18, 2007 3:26 pm

Here's a pic of the obx downpipe. You can see the where the o2 sensor goes

Adionik · Post by **Adionik** » Wed Apr 18, 2007 4:22 pm

Is that OBX downpipe pretty loud? I've heard some bad comments about it...

jckevns · Post by **jckevns** » Wed Apr 18, 2007 5:11 pm

I just laugh cause when I had it installed I was running just the obx header and the downpipe
So it ridiculously loud when I had it on my car

Cruisin04Neon · Post by **Cruisin04Neon** » Wed Apr 18, 2007 8:01 pm

Thanks for all the info. PS i did mean .020 over too.

Any thoughts on gains on just increasing the bore? with rods and new pistons?. not other mods ect. intake and exhaust

thanks

OB · Post by OB » Thu Apr 19, 2007 3:02 am

It really depends on what pistons you go with. Raising the compression will gain some power, especially with a good tune. If you retain the same compression, dont expect a huge gain. Keep in mind that if you plan to boost the motor someday, you'll want to run lower compression. If youre preparing the motor for turbo, this is the way to go, but will result in a loss in power in the meantime.