Port matched intake and swapped to 4-2-1 header and lost power

[scirockinit]

82 rocco. With stock exhaust manifolds. Swapped in 4-2-1 header and port matched intake manifold on tb and head side and got rid of spacer for neuspeed tb. I feel I've lost power. Do I have to adjust anything now that I've done this?

[Jettaboy1884]

What other modifications do you have? I assume you have something other than a stock exhaust, right?

Any K&N panel filter, or cold air duct to the airbox?

I did nearly the same thing back when I had my '83 GTI and didn't really feel a noticeable gain, but certainly not a loss either...

Did you do any sort of timed acceleration before and after?

[scirockinit]

3in intake tube. K&n filter. G grind cam. Adjustable cam gear. Neuspeed big bore tb. 2 1/4 exhaust cat delete delete side exit. Bousch super plus plugs, bousch high performance 8mm plug wialso this header I swapped to came from a 79 scirocco. I had to remove my 02 sensor, so it runs a lil rough thru low rpms.


After making,a video before and after of accel I've noticed a differemce. Previous my 0-60 was about 8.5 now its about 6.7. Ive lost that low end torque but now I have a response all the way thru the peddle

[teknikALLEN]

Loss of low end torque is what you would expect with this engine with those mods, with small gains in HP and more so torque in the high RpMs.
I think adding an O2 sensor will improve the fuel air mix and perhaps add a little low end and smoothness... I may be wrong though... there is some stuff by Scientific Rabbit that was helpful...
snark free zone.

[Glegor]

3in intake tube. K&n filter. G grind cam. Adjustable cam gear. Neuspeed big bore tb. 2 1/4 exhaust cat delete delete side exit. Bousch super plus plugs, bousch high performance 8mm plug wialso this header I swapped to came from a 79 scirocco. I had to remove my 02 sensor, so it runs a lil rough thru low rpms.


After making,a video before and after of accel I've noticed a differemce. Previous my 0-60 was about 8.5 now its about 6.7. Ive lost that low end torque but now I have a response all the way thru the peddle

wow dude, welding an o2 sensor bung on the header was too much work, so you just deleted the sensor all together?

thats a GREAT mod for improving your POWER and ECONOMY..

[scirockinit]

Um no. my other rocco runs without one I figured mine would be fine as well. I don't have a welder and didn't realize that there wasnt a 02 sensor until I had it all together and went to attach it.

[ps2375]

What 4-2-1 header do you have? And way back in the day when I went from a stock dp to a header and then eventually went to a tt dp, I was amazed at the low-end TQ that I gained(compared to the header, not to mention mpg) and I didn't lose much at the top either. Prolly had more area under the curve with the tt dp.

And you could tune it with a wideband to get a good afr and leave the sensor out, the CIS will hold the set mixture very well throughout the rpm range.

And bigger is not always better for certain parts of the intake and exhaust, it is generally better to not go too big and maintain higher velocities of intake air and exhaust gasses than to slow them down with oversize tubes/pipes. That could be where some of the tq is being lost.

[ny_fam]

Here is a real good CIS tuning setup I use.
http://forums.vwvortex.com/showthrea...and-controller

Also a common miss conception when modifying a engine for more power or to be faster is that peak power is faster then power through out a wider rpm range.(except drag racing with proper gearing to only run in the power band rpm range)
A car with a steep power curve near high rpms - feels fast due to the rapid power gains as rpms rise but is slower than a car with a lower peak power but wider power band rpm range.

Cheers
ny_fam

[ziddey]

Your other car may have had the idle mixture set better than your current one. The ECU was able to compensate before with the O2, but now that that's out of the equation, you're stuck with whatever the setting is. Get a bung welded in, or tune with an exhaust gas analyzer.

Hell, since you have no cat, and hopefully no exhaust leaks, you could try throwing your o2 sensor into the tailpipe and providing 12v to the heater to get it online. Then use a voltmeter on the signal wire and set the mixture that way. Aim for 0.7-0.75v to start. Take it for a spin, and fine tune from there.

[vr2jetta]

I just bought a cheap ebay header that didnt have a bung either. I do however have a welder but I still had to find the bung. Any exhaust shop should have one, and if you bring your header in there also, they will probably weld it in for you. You'll walk out spending around $30 I bet, but your lamda will be operating properly.

As far as power loss I agree with other guy....Loss of low end torque, gain in high end hp.