power upgrade
 

Hi
I am exchanging my car for a mazda rx7 13 B series 4 I believe; what the best way to gain lets say 50 or more brake horse power without breaking the bank and keeping the injection system ?thank you

I don't believe there is a "best way" to cheaply gain 50hp in a NA car.
It is what it is and you should optimise what ya got and live with it.
You need a turbo if you want to play at adding HP.

I have read infrom the racing beat site you could have the engine ported, you could get a freer flowing exhaust; and they say with this sort of changes you can gain 20 /100 more bhp,that's why i am asking ( i think they also say you need to get a new carburator; porting seems cheap, but the exhaust is, for me expensive, as well as the holy carburator.), and to go from injection to carburator is not, for me , a good idea. But i would have liked to know if what they say is real

Welcome to forum

I think you are making the common mistake of conflating HP with speed.
Unless your goal is to compete in dyno competitions, change your approach.
You could add 1000 hp and if your tires are bald, you've gained nothing.

Optimize your suspension, brakes and tires and you've improved real world performance.
Make sure your engine is running at tip top spec.

I know this is not a very sexy response, and probably not a very popular one either, but it is firmly grounded in experience.

I agreew ith this; i did that with my 1986 mr2 aw 11 ; lowered suspension; wheel spacers; new bushes; good tyres; and then someone put a 180 bhp 2 zz in it and it was good, and light, because it weight less that the mazda.....So with the weight of the mazda, and if at the same time i improve the handling, i'd like more hp cause of the weight; by the way, the transformation we did cost me 8000 $.....I'd like to spend less on the fc.....

Do the exhaust. From what I've read on here a long primary system is probably best. IMO don't switch to a carb look at a standalone EMS instead. The Haltech Elites look nice but they're pricey. Cheaper options exist like Megasquirt. Browse around here: https://www.rx7club.com/engine-management-forum-37/
Though more money than a carb setup the end results are better. Unless you have lots of money to spend I wouldn't necessarily tear the engine down just to port it. To gain 100hp would probably take a bridge or peripheral port which will require custom intake manifolds. Sure the stock intake will bolt to a bridge port motor but it won't flow enough to get the ports full potential. You'll need a standalone for either of those ports as well. I don't know about a S4 but 200whp seems to be the ceiling on the stock intake on a S5 and that takes a lot of work. 180 seems more realistic. You might be able to break 200whp with ITBs and a streetport. Browse around here as well: https://www.rx7club.com/naturally-as...nce-forum-220/

Long story short. Listen to clokker or go turbo if you want power.

Thanks. When i wrote 20/100 bhp power i meant 20 per cent more than the original power which is meant to be 150, so that would be an extra 30, which would make 180 bhp. I am having a look at the threads you mentioned