O.k That was weird, this forum has been acting up heaps.

What I said was,
I know this is a stupid question but why is it that a different carb, such as a webber, makes more hp then the standard nikki (assuming both are tunned properly)? Also how much more power would I expect to get if I went to a better carb such as an IDA webber?

 

Simple answer is more airflow.

 

o.k, What is the best carbie for an rx-7?

 

i've heard nothing but good things about the mikuni carbs. look that one up.

 

The carb is only one part of the engine. Ideally each part should match. Remember Henry Ford was more concerned when parts did not break- it showed they were over=engineered and therfore too costly!

With the 12a, the stock Nikki will cope with airflow/fuel up to about 150hp, The limitation is the exhaust system particularily the header.

To go above about 150 hp the ports will have to be opened up. The siock carb and fuel pump are now the limitation. A modified Nikki is still the cheapest option to about 190hp. A higher performance carb becomes an option only at the top end of streetport performance.

Above about 170hp the typical street port is reaching its limit, so the next step up is a bridgeport, when you will definitely need to consider what high performance carb should be fitted.

The four choices are Delorttos, Holley, Mikunis and Weber, They are all good designs, all have experts who say they are the best. The reality is they are the best because that expert knows how to well set up that particular make. All can give you good performance in the 175-250hp range, if they are jetted right. Some are easier to tune but with an expert there is little difference in output.

However if you look at the top engines, the most common is the Weber IDA, 48 or bigger. Perhaps a bit difficult to tune for low revs but certainly capable of optimal power for a high performance set-up.

My preference is for a Nikki with a stock port, a modified Nikki for a street port with possibly one of the others if you get a bargain secondhand, but once you go bridgeport look at the IDA. K&N air filters help in all cases!

If you added an IDA to a stock set-up your performance might even go down! Select the carb for the set-up you want, in simple terms match it with the porting and header/exhaust.

 

Do K&N make an air filter that will fit an rx-7 without any modification?

 

yes.




PAUL: so are you trying to say its only worth fitting an aftermarket carb if you are going over 150hp?

 

Yes K&N sell an filter filter which will fit the cleaner of a stock Nikki carb. It improves performance slightly and while initially expensive its reusable after cleaning and oiling.

 

Thorin, yes I think that if you are only doing bolt on modifications a Nikki is best. You can get it modified, including mechanical linkage of the secondaries, quite cheaply. The high performance carbs add very little until their potential matches actual airflow need, thus are not worthwhile unless you score a cheap carb and manifold.