Even with a turbo the larger the passage you're pushing the air through the easier it is to fill the cylinders, the more efficient your turbo is and the easier it can work.

To get the benefit you also need to "port match" the NA throttle body bore to the intake. The turbo intake has a smaller throat where the throttle body bolts up so to be able to operate the throttle the hole has to be increased to the diameter of the NA body.

The other thing you want to look for is a throttle plate that doesn't have the plastic "****" on it.


Everything you needed to know and pictures !!!
850 Na Throttle Body Swap - Performance Modifications - Volvospeed Forums

 

thanks brother, so l can pick up an N/A TB from the junk yard but l will have to get a different intake hose to fit the TB that runs to the intercooler. what plastic **** are you talking about? whats that?

 

The ports on the head are the same size, so getting a bigger throttle isn't going to do much... It can only flow so much and is limited by the smallest point.

Take a 1/2" copper pipe and step it up to a 3/4". Then step that to 1" and then 1 1/2". Keep going as big as you want, the whole thing is limited by the 1/2" part.

 

In your example it WILL flow better than the same length of only 1/2" pipe all the way. Once through the length of 1/2" it "sees" less resistance. You wouldn't have higher pressure at the end of the 1 & 1/2" but you would have more volume. And volume and pressure is what we're after.


But IMHO you're doing that backwards.
With my 850 I'm starting out with the sky, pulling it through the intake, air filter, turbo, then pushing it through more tubing, intercooler, throttle body, intake manifold, head and past the valves.

Building a performance engine is like putting lights on a Christmas Tree. You start out pretty good and see an area that needs just one more string. In the end you're taking out a loan to the electric company.

Yes the stock intake runner port is smaller but there are five of them needing to be feed through that one throttle body opening. Because of cam timing you have two (maybe three but I'm not going to do the math on a 5 cyl for this) sucking air at the same time.
In mechanical engineering there are tables for pressure drop per foot related to length of run and diameter of run in fluid dynamics. It's how they figure out what size pipe they need to run the water to your second floor shower. Same applies to air pressure. You may have 10 psi boost right after the turbo and if everything is sized right you many not lose pressure but it doesn't mean you have enough capacity (CFM) to flush and fill the cylinder. Like the average 110 volt home air compressor pushing 125psi but you can't really get that much volume.

Back to the Christmas Tree!! Each time you improve something you start looking at something else. This improvement alone with the "clean" throttle plate will give you seat of the pants improvement in throttle tip in from idle. If you later port match the intake to the head and port and polish the heads runners you get that much more benefit. It's all about volumetric efficiency.

"" It can only flow so much and is limited by the smallest point. ""

Yes and NO!! That is the beauty of the turbo. No matter what the smallest point is if you raise the pressure at that point it will increase the volume coming through that point.
But if you increase the size of the smallest point or any point in the system you are still lowering resistance and increasing the chance of getting more volume at a subsequent point.

Or maybe I just need to put the crack pipe down

 

The intake hose that will fit the NA throttle body is only available from Snabb
NA Throttle Body Hose for Turbos 93-97 850
That's the only place I've found them so far.
The linkage is different and you can also get that from Snabb or make one.

If you pull your intake apart at the throttle body and then open the throttle plate you will see that "****" on the throttle plate. It's function is to restrict intake right at off idle but being on the throttle plate it restricts flow all the time. It makes for a smoother daily driver take off from a stop.

If you take a look at the two throttle plates in the picture it should pop out at ya.

 

I guess the other way to look at this DIY mod is that it's mainstream enough that you can buy it for $370. I'm guessing if it's a commercially available bolt on kit there's more than a few people thinking it does some good.

Big Bore Turbo Intake Kit

 

In my pipe example, I meant for the flow to be the other way from the 1 1/2" to the 1/2". If you port the head to the intake, then yes, you will get the most out of these other modifications. I didn't see anyone mention porting the head though.

 

So question for you. So lets talk about one intake port and not modify it at all, just leave it like it is. The size of the throttle body is obviously larger than the single intake port, right? Therefore why would we need to go any larger? The answer is we dont. But, add 4 more intake ports and the rapid volume of air supply needed to supply these 5 intake ports does exceed area of the throttle body.
Volvo supports what Kiss said, they said since we are forcing air into the intake we do not need as big of a throttle body. If pressurized air did not have the ability to flow more they would have left the throttle body at the larger size.
Another supporting topic, an air compressor. Air compressors are measured in their ability to produce amounts of continual air supply at specific pressures. The release of that air is a combination of valve size and supply before the valve. If a compressor is pressurized with a small release valve it does not have the same CFM as the same compressor with a larger release valve.

Experiment:
Take two gallons of milk in plastic containers.
Pore one of the gallons into a pitcher.
Take the other gallon in one hand and the pitcher in the other. Make sure the gallon of milk in the plastic container has the lid off and the pitcher is open too.
Turn both upside down at the same time then report back as to which one moved the milk the fastest.

Experiment 2:
Buy a third gallon of milk, tap a compressed line to the container and pressurize it. Remove the lid.
Report back if the milk left the jug faster

 

yall talking scientific talk which makes me lost. dont get what you guys are talking about.lol, so does a bigger TB help the car have a better pep from a stop? do l have to do any modifications to my car when l switch to a bigger TB?

 

Worse case you will throw a cel but the car will adapt to the new airflow.

 

Slimflex2, Yes you would get more pep with just removing that chunk of plastic on the turbos stock throttle plate.

The bigger throttle body is more for increasing the top end.

Do you think the diesel throttle body is bigger yet ??

I wish we had diesels !!!

 

Who's payin' for all this milk


I'm sticking with Snaab sells it for $370 and I haven't seen a complaint.

 

I noticed it mostly on the bottom end from a stop. Same driving style with na vs turbo tb I was breaking the tires loose where as I wouldn't before. A lot peppier from a stop.

No CEL. Just get an NA intake manifold and throttle body, no reason to keep your turbo manifold and bother with port matching.

 

The milk example is different. Take an empty gallon of milk and an empty pitcher. Take two one gallon pitchers full of water. Pour one pitcher into the other. Pour the other into the gallon of milk, with a smaller opening.

 

hahahahahaha, thats a good one. you are one funny guy.

 

Sooooo, are you then saying that Boxpin, I and many others wasted our money on our 2.5" or 3" exhaust systems since they are way bigger in diameter and flow than the stock exhaust and massively bigger than one exhaust port

 

@ kissforafrog, let me ask you. do l have to do any modification when switching to N/A throttle Body?

 

Can I answer that?

The Turbo manifold has a smaller physical opening than the N/A manifold. If you move to a N/A throttle body you will need to open up the Turbo intake manifold to match or replace it with a N/A intake manifold.

No other modifications required.

 

No.

The engine only needs so much air. My point was that just swapping a throttle and intake will give very minimal gains. The valves will only open so much and the ports are only so big.

If you swap a bigger cam into a head with bigger ports, you can take more advantage of intake and throttle modifications.

 

Did you read this ??
850 Na Throttle Body Swap - Performance Modifications - Volvospeed Forums

Everything in this kit. You need to have a NA intake manifold or enlarge the port for the NAs throttle plate to work on your stock turbo intake manifold.
Big Bore Turbo Intake Kit