I didn't know that swapping on a NA throttle body did anything to help performance.

I know that the NA throttle bodies had a plastic plate in them that reduced air flow at WOT so people would remove the throttle plate and install the plate from a 960 in the NA throttle body to help them preform a little better.

I sure hope you're not chasing someone's myth.

400 grit or higher is effectively polishing. You don't want a smooth surface in the intake tract; leave it a bit rough for better flow and fuel atomization. If you want to polish anything, do the exhaust ports. On the exterior, whatever, knock yourself out.

RSPI; ck out this thread on the topic; the N/A TB is 10mm larger in diameter than the turbo on the OD (ID of attaching hose). Yes the N/A plate has a plastic bobble on the plate to smooth flow during initial transition, most guys grind it off and solder up the remaining holes, or put in a 960 throttle plate (which is sans the plastic piece). The effect of the plastic piece at WOT would be negligible if anything.

https://volvoforums.com/forum/volvo-...re-air-64027/?

So, one would do this to take on more air for a ECU upgrade? What would it do if you had no other mods?

Yeah, I don't know if I'd recommend any of these mods (N/A TB, N/A cams) w/o an ECU "tune". I have both installed in my 855T and am driving it now, but am taking it easy until I drop in the green ard tune. And I am waiting on AFR (air fuel ratio) gauge before I do that. ARD recommends monitoring AFR and boost when doing a tune, so I got both gauges coming from AEM; should be here next week...

When installing the NA throttle body you are still pulling the air through the MAF so you don't need to have a tune. Most of the time you are running on vacuum so what it's doing is allowing less restriction to air flow at that point. It's a little bigger in diameter but after all it is the stock Volvo throttle body that's used on non turbos. Same with the cams. They aren't that radical that the stock ECM won't adjust easily. They are stock NA cams and just allow for a slightly longer period of the valves being open and overlapping due to a stock NA engine requiring a little more time. In a turbo it will likely cost you a little (very little) gas mileage due to the extension of the timing but it rids the cylinder of exhaust better and fills the cylinder more effectively as it has a little more time to do it.

Going with the smooth throttle plate instead of the one with the plastic "lump" gives better response off idle. Being front wheel drive and if you are modified having more response right off idle isn't necessarily a good thing. At the top end it allows for a larger opening and a smoother path as the air doesn't have to go over and under that lump of plastic.

But to really use them you also need to have a free flowing exhaust. Once you have a way out the throttle body and cams make a bigger difference as does a bigger turbo. It's all about increasing it's ability to breath and you need to look all the way from in front of the air filter to exhaust tip.

Tuning can optimize these mods but you need to remember a NA runs these components, throttle body and cams stock and they aren't that different from the turbos.

I'd have to say that a ~10mm difference in diameter is a pretty big one under the foot. Especially with all that pressure through it.:D Good news is that I found an OE hose at the junkyard in good enough condition for me to use. I stretch fit it to the TB and I was in luck. Bored the mani and slapped it back together with the NA TB using original the "puck plate" and took her for a test run. The difference is astounding off the line, even WITH that hunk in the way. Can't wait to get that snabb hose and 960 plate on!

I believe it is a valuable improvement and it's why I had Rspi grab me a 960 throttle body months back.

And yes when you look at the two next to each other it's a difference but it's one of those things that isn't drastically changing anything the ECM can't compensate for as you are still pulling air through the MAF and it's still calculating the correct dwell for the injectors. So you don't need to "tune" to get an improvement in fun but if you did, you'd get more bang out of it.

If you haven't done it yet you might want to think about going to the 53-55psi fuel pressure regulator unless you're going to go to bigger injectors. Going the 10psi up is like going to one size bigger injectors. I did it shortly after purchasing mine as I had a fuel leak in the line leading from it and as long as I was going in, I upgraded. It's another thing the ECM can compensate for. It just runs the injectors shorter "ON" times to adjust for the higher pressure. It gives you a little more ability to supply more fuel at higher RPMs if needed. I didn't and still don't have any driveability issues or loss of mileage.