Guys my nitro engine came with 6mm & 6.5mm & 7mm Aluminium carburettor inserts..

Can someone please explain to me how using different size insert would effect the engine output and fuel use...


Example
would fitting the smallest 6mm insert give me lower or higher or the same bottom end power output ?

Think of an engine as an air pump. The more air you're able to move efficiently, the more power it will make.

Pretty much what socket said...

A smaller restrictor will help with low end throttle response, but it also increases the speed of the air going into the engine possibly making it harder to drive/ tune. Most engines have a "happy" size where it works the best. Going to big or too small really affects performance. stick to what the manufacturers recommend. It makes life easier

So I have dyno tested this quite a bit , Smaller inserts reduce power and RPM quite substantially , all big block engines i have tested wont make full power on anything less then a 8 mm insert, some even need a 9 mm to fully open up. nothing makes full power on a 7 mm and and how much power is lost going down from a 8 mm to a 7 mm depends on the engine... typically the more powerful the engine is the more negatively it is affected by the smaller insert....Whereas the milder the engine the less it is affected by the smaller insert.... So a Mito 7 is going to take a much bigger hit in power then will a Mito 4.....Run both those engines on a 6.5 insert and they will make very comparable power and RPM to each other but step both up to a 9 mm and the Mito 7 will absolutely blow the doors off the Mito 4......The Mito 7 is a much more powerful engine but unless its allowed to properly breath it will never see its full potential.... The 6.5 insert acts like a governor on the throttle restricting the amount of air the engine can ingest and becomes a very substantial limiting factor in performance to some of these higher powered engines.....

i just tried switching my modded b5 from the stock 7mm to a 8.5. before the motor ran great but always lacked on the second half of the straight, only time it would really run out was if it was pushing the edge of being too lean but when i switched to the larger restrictor it pulled all the way to the end and sounded great and still had good smoke. that will be what i run from here out in that motor.

So you're saying if I go from the 7mm to 8mm in my Samurai it will pretty much be insane.

How much do you see fuel mileage dropping though? Just curious. Most of the local guys are running 6mm in their OS based motors and pulling 11-13 min depending on the track / driver. With my 7mm I get about 9 1/2 min

others can speak on their mileage results but i'm getting pretty close to the same if not more but i didn't run a clock on it. guess it really depends on how well you control your wheelspin. i'm getting between 10-11 minutes in the truck but upper 9's in the buggy but i'm struggling with getting the buggy hooked up. its over 10 in the buggy when it was planted. keep in mind i'm still not running at a full race tune, still a tad fat.

it will go faster on a 8 and even faster on a 9mm....... most guys dont see a loss of mileage, some even see a increase..... But some say they see a loss, but not sure how many actually test back to back....

Where can I get an 8.5 mm venturi that will fit my werks carb? I want to test it out on my mod b6. Currently I am running a 7mm venturi.

i got mine from amain on clearance over the summer but it's showing discontinued now.

well I'll just have to try it and see

I have another question, I saw that Protek offers elliptical shaped venturi as well as standard round ones. I've never used anything other than standard ones. What affect does changing it to an elliptical have? for example 7mm elliptical vs 7mm standard.

Correction, my Samurai comes with elliptical (just noticed that).

I agree on trying it. The samurai came with 8mm and 7mm, so you have the option, of course they're both elliptical.

Will os or novarossi inserts fit werks carbs?

from what i understand the nova ones fit but sit high in the carb.

The elliptical inserts move the incoming air over to the side and over the spray bar, to help with low speed/ off idle runability...

I have been using the Nitromizer inserts for a while and did notice that with the normal insets, cruising around at just off idle, the engine loaded up. Now, this isn't ideal during a race to drive like that, I just wanted to see if some of the claims were true..... and they were