1990 Corolla Dx 4Afe

[Grimey Connor]

I just bought this car a few weeks ago, its got a bit of wear on it but i love this car, it runs amazingly with 165k

i would like to improve the horsepower as much as i can but do not have much money.

I have a K&N cold air intake and i wanna know what all i can put into this vehicle to get a good amount of power from it without an engine swap. I plan on putting an aftermarket exhaust on it in time,

what can i put into the engine to help that is not going to cost way too much right now?

[Kiwi-Corolla]

Congrats on the purchase. The 4A-FE was built with economy in mind, which means it's hard to extract power from and doesn't respond very well to modifications. Since yours is the 1990 model it will be the 6th generation Corolla (AE9*), fitted with the first generation 4A-FE, which are unfortunately down on power from the second generation 4A-FE which were fitted to the AE10* series Corollas. There are a few things you can do to give the engine a bit more pep, but at the end of the day if you want to see any real performance gains then an engine swap is in order. Does it have a 5-speed manual transmission, 3-speed automatic or 4-speed automatic? The 5-speed manual is the quickest of the three, with the 3-speed automatic being the slowest.

First thing's first, your intake. I see you said that you've got a K&N cold air intake. Is this a true cold air intake where the air filter is located outside of the engine bay? If not then this is restricting your power from the get go, as short ram intakes (where the air filter is located inside the engine bay) sucks in engine heat. Colder air = more power, so the colder your intake charge is the more HP you'll make. This is the reason why cars perform better during cold mornings as opposed to the heat of the day. If you currently have a short ram intake then I'd suggest switching to a cold air intake. You can still keep your K&N air filter (providing it's the pod filter style and not the panel filter style), but you'll have to buy a couple of aluminium pipes and route them to the passenger's side wheel well. This will allow maximum air-flow of cool, continuous air. The only warning is to never allow the filter to be fully submerged in water (in other words, don't drive into a puddle that's bumper height). Splashes from the rain water whilst driving or from the hose while washing the car won't cause any damage whatsoever though.

Here's a link to a post I wrote a while ago explaining the procedure:

http://www.toyotanat...tml#post3259718

And here's a DIY that another member made based on my instructions in the above link:

http://www.toyotanat...ce-bicycle.html

Please note that both of these links are for the 7th Gen Corolla with the second generation 4A-FE engine, however your first generation 4A-FE will be very similar.

Pics of my actual set-up as it is right now:

The next point of call would be your exhaust. From factory the exhaust piping size is 1.75" OD (outside diameter). This is very restrictive, especially with the catalytic converter in place. The cast iron manifold is also very prone to cracking through the middle with age. For the 4A-FE I wouldn't recommend going any larger than 2.25", or else you'll lose too much back pressure and actually reduce the power. Removing the catalytic converter will also yield a smidgen more power, but it is illegal in a lot of countries and may cause you to fail your roadworthy/smog tests etc, so make sure you check with your local authorities before removing it. You can buy full pre-made exhaust systems, high-flow catalytic converters and 4-2-1 exhaust manifolds on eBay, all 100% bolt-on, or you can get your own piping custom made. Either way, be careful not to go for piping too large in diameter or a horrendously large/loud muffler.

Apart from that there really isn't a whole heck of a lot you can do to these engines performance wise. The only other thing you could do would be to remove any unnecessary weight from the vehicle, such as the rear seats or the spare tyre, however this will increase road noise and you won't see any noticeable gains in terms of power. You'd be much better off focusing more on suspension upgrades to make the car handle better, otherwise you'll be pouring money into an engine that unfortunately just won't give you the results you desire. Best of luck, and enjoy your new ride! :)

[Tibs]

What he said, great reply post :-)

[Grimey Connor]

unfortunately i bought a 4 speed automatic, still love the car, just hate automatics usually.

your post was extremely helpful, thank you for this, i had been waiting for so long.

i took off the stock intake box and attached the new intake to the original tube. but with this info i will work of getting it set up like you have.

i will post a picture up if you or anyone feels like giving advice towards what my motor looks like.

time to go replace my spark plugs lol thanks man

[Grimey Connor]

what do you think if until i can set up that intake correctly, if i get a tube and take the start at or around the grill where the air flows in good and had the end of that come up to the intake? would that be completely pointless?

[Grimey Connor]

what do you think if until i can set up that intake correctly, if i get a tube and take the start at or around the grill where the air flows in good and had the end of that come up to the intake? would that be completely pointless?

[Kiwi-Corolla]

No problem mate. Routing ducting from the grille area to the pod filter isn't a bad idea in the meantime, until you install a CAI, but the engine bay heat will still be sucked into the short ram intake, especially at idle. For my very first intake set-up I used a short ram intake and used ducting and bellmouths to get more airflow to the filter, but in the end nothing compared to the CAI :)

Here's what my old set-up used to look like a couple of years ago:

[Gabo]

Hey Kiwi-Corolla! 
I really like your modifications and  I'm very lucky to find your post because currently I'm working in the same way as you did with the routing duckting. (I didn't find any same solution on the internet). My idea is build aluminium box(heat resistance box) for the duck and the air filter because I don't want to suck any water through CDI and this solution I think a little bit safer. What do you think, Can I reach a "similar" performance with this solution? OR what is your experience with the water sucking? I hope you're still here 🙂

[Catlover]

Gabor, welcome to TOC UK

Kiwi-Corolla has not been on the forum since May 2015, so you probably are not going to get a reply.