ST / 7afe tuning possibilties summary., The basics theory wise. Options

[youseman]

THIS IS JUST A SUMMARY

Theres alot of people throwing opinions around about the 7afe's tuning capabilities and since I'm a mechanical engineering student I thought I'd just unload some basic info into one place .

Unfortunately as I have only just bought a celica I cannot speak from personal experience but I can speak from some of my friends. I have also done ALL my homework online.

The 7A block and FE head are matched by toyota for one purpose. To give reasonable performance and great economy for the entry level of the 6th gen Celica. The 7afe does exactly this, it's not built for serious performance, its meant to be just enough. The 7A block has an oversquare bore to give excellent torque characteristics at the expense of high end power. The FE head is a narrow valve angle (22 degrees) economy head, that is to say, its designed for low down torque, good fuel economy, and overall tameness. The 7afe engine only actually uses 60% if its capacity at full power.

"The 7afe is a weak engine" is partly true, although it has a forged crank, the pistons and especially the rods are attrociously feeble. Sure they can handle the stock 114 ponies, but they won't last very long under more power.

Aside from your basic N/A tuning options, which in my opinion arent really worth the money, your tuning options come as such:

Head Swapping
The 4age or 4agze heads are a viable option, they provide much less restricted intake and in the gze case provide a little boost.

Engine Swapping
Probably the most cost effective, but if, like me, you live in the UK this is no longer really possible as the DVLA have legislated engine swaps into the £4/5k region.

Forced Induction
(Make sure you understand turbo setups or this will mean little to you).
If you have an ST then this is your best option in my opinion. There are numerous 7afe corolla turbo kits which, with a little modification, will fit the ST.
If you plan on running low boost (below about 8 psi) it is possible to use stock internals but do so at your own peril.
This is my reccomendation for tuning a 7afe engine:
Most importantly you will need forged internals, Pauter rods would be my choice and a forged piston set. The later can be imported from the states at http://www.importperformanceparts.net/imports/pek-geo.html. This includes a copper gasket as well as some other useful items to reinforce your block.
After this, a turbo set-up including a BOV to avoid compressor surge and an intercooler to keep intake charge temperature down will be a relatively simple job.
Make sure you have this checked and the map created by someone who knows what they are doing, or you will find you engine in pieces relatively quickly.

This will allow somewhere in the region of 200-250bhp reliable and without any excessive risk to the engine. Higher boost may need better valves, sparks, etc, to avoid melting them.

Up to a certain boost level, all the turbo will be doing is allowing the engine to utilise its full capacity, past that its effectively increasing the capacity by increasing the amount of air fuel mix you can burn.

I will reccomend forged internals for any engine, tuned or not, simply because they WILL NOT break unless your run crazy boost. And are a MUST HAVE for high level boosting.

I will be using forged internals and a turbo set up when i have enough time and money to get tuning, I will be running a progress blog so otheres can see.

P.S. Keeping a FE head will still leave great fuel economy at low boost if you find yourself very skint at some point.


Also, i will not be held responsible for any damage you do to yourself or your car using this info, it is for that purpose only, info.


This post has been edited by youseman: Oct 13, 2009 - 1:42 PM

[youseman]

I read that overboosting was wastegate related at first but three people (one of them being my lecturer) all swore blind that overboosting and compressor surge were the same. maybe they're all retarded but you can't blame me for thinking that. and i was refering to an engine as an entire unit, dont need fluid mechanics to know where the excess boost is gonna go. perhaps i should be more exact with my phrasing round here