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

[SwissFerdi]

Good stuff. I would love to see a detailed blog on turbo'ing a 7A-FE, as it sounds like a feasible option for me. So from what I'm reading, you don't absolutely recommend forged internals for less than 8 PSI?

[OOBE]

^ I already told you that it's not needed to do anything to the engine for 8 PSI. No need to be a mechanical engineer. Just experience with the engine.

[SwissFerdi]

I know man, and I appreciated that. But I'm trying to hear as many opinions as possible, and I'll probably be asking again.

[youseman]

as oobe says, expeirence says the internals will hold at 8 or below, although i would worry personally, having seen how thin the rods are. anything over that you MUST get forged internals.
when i do the turbo I will do a detailed blog and list all my part sources and prices etc. that wont be for about a year yet though

[celica3000]

in 2005 i buy a turbo kit from corolla(7a-fe) from usa
today i drive the car with 0 problems
i have internals stock

[FunkySR]

I live in the UK, and I have the limited edition SR. I have a turbo conversion with stock internals and running 10psi. I got 160 whp @ 6.9 psi. Almost 2 years and no problems and I use this car everyday....all 192k miles of it.

J

[youseman]

good to here stock internals hold well! i personally would feel more confident with forged, but oh well.
funkysr, where in essex you from
?

[Wintersun]

Youseman are you on celica-club.co.uk?

[FunkySR]

193k miles and counting. i'm from Thurrock.

[youseman]

possibly, can't remember, i signed up too a few forums, but this was the one that caught my attention.
funkyr: ah kool, im just over the river in dartford

[lagos]

You need a four wheel drive trans to swap a 3sgte?
A bov prevents overboosting?
Accurate documentation is the basis of good engineering, also...math.

[OOBE]

youseman, no offense but you cannot expect anyone to take you serious when you say a BOV prevents overboosting and that you need an AWD tranny to be able to use a 3S-GTE. Also, one year is a long time, so why open this thread now when you're not even starting yet? No offense, but most of the 7A-FE info you wrote is old knowledge here and has been written many years ago.

My biggest question is why are you talking about an engine that you have no experience with? Hearsay doesn't count. Seems to me like you came in here out of nowhere to brag about being a mechanical engineer. Not stirring any arguments, just wondering about your purpose of this thread.

[youseman]

oobe, why don't you try running a high boost application without a bov and watch every compressor surge bring your engine closer to destruction?
i put this thread up cos this information was all over the place, yes it was already here, but i was sick of searching endlessly for one little bit, so i decided to put it all in one place, as it says if you read the article instead, and no offence meant here, being a jackass?

[OOBE]

Getting compressor surge has as much to do with boost control as fudge brownies have to do with coronary artery bypass surgery. Why is that? A BOV has nothing to do with overboosting, wheter you're running high boost or low boost. All it does, like you already know, is release unused compressed air to prevent it from returning to where it came from, the turbo, and cause compressor surge.

Now that this is clear, why are you associating compressor surge with overboosting? They have no relation. You can overboost with or without a BOV, because the BOV's job is not regulating boost, but liberating it once the throttle is closed. A wastegate prevents overboosting, which again, has nothing to do with surge. The wastegate works with the exhaust gas, which you should know, while the BOV works with the air charge.

By the way, compressor surge doesn't "bring your engine closer to destruction". That is so dramatic. You should write for a car magazine, LOL. It does nothing to the engine. Why? The compressed air is not getting to the engine. Its entry was denied. The door was closed in its face. "Get outta here, boost. I don't need ya anymore". So the boost, feeling all sad and rejected, returns back to its mother, the turbo, and takes it all against her, making her spin in the wrong direction and if its mad enough, snap off her neck. Any questions?

[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

[delusionz]

hes right youseman, you are using the term overboost differently than we normally mean by the word.

what you're talking about is where the turbo is compressing more air than the engine itself can digest. this is just 1 means of getting compressor surge, and a bov wont help you there as this compressor surge would happen at full throttle, a bov releases air when the throttle is closed so obviously you dont want it to be releasing air when your on the gas.

overboost as we know it is simply when you're driving a factory turbocharged vehicle (or using the ECU from one), if the boost goes up higher than the factory setting then we call that overboosting. if you overboost too high you get boost cut (or fuel cut)

[Rusty]

nice bits of info, just wondering though, if anyone here are running 7A-GTE's???
heres a dyno plot with a 7agte (though its properly some racecar )
http://i16.photobucket.com/albums/b20/Matt...20V/440hp-2.jpg

[youseman]

ah touché, i was told overboosting was the turbocharger forcing more air in than the engine can digest/more boost is required, hence the bov point. I will have chat with my lecturer. He's a materials scientist teaching vehicle dynamics, "go figure" i believe is the term; i would have thought the guy would get his facts straight before lecturing on it. Maybe in engineering its different, but i doubt it. however i don't appreciate being patronised oobe, wether i may be right or wrong, try to have some respect for people please bro.

[SwissFerdi]

I think OOBE was being decently polite considering you called him a jackass.