This is not a girlfriend comparison thread! I was thinking about upgrading my m20b25 (low comp.) gradually. My thoughts were to upgrade in the following order, but I 'd be interested in hearing from people who would do things in a different order and why. Mild chip, exhaust manifold (standard exhaust system), cam and gas flowed cylinder head. They would not all be fitted at the same, rather fit one upgrade, then upgrade the following component a month or two later. Have I chosen the best order to do things in terms of bang for buck?
The main purpose of this thread however was to find out where people are sourcing their modified heads from. Are there any suppliers offering gas flowed m20 heads off the shelf? Which suppliers/machinists offer the best product for the price in terms of quality and performance gains? And lastly, what sort of gains would you expect to see from a well modified head alone?
Good head
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maggspower
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Sadly, you will not see great gains from any one item or upgrade alone, a decent tuned engine will have selected parts that will work together and compliment each other. Spending good money on components is one thing putting it all together to work as a package is another.
Unless they have been done to your knowledge, get your injectors cleaned. Make sure your engine is running well and is healthy. There is no point in tuning a rattley worn out turd of a motor.
My personal suggestion would be, a chip (speedtouch), BBTB, and a lightened flywheel, as a first stage. The throttle and flywheel are future proof, as in they will continue to work with any further mods that you do, as will the chip be to a certain extent. You will see a considerable change in the charcter of the engine, much quicker throttle responce, and acceleration in the lower gears. The time it takes the engine to rev down will be less, making it nicer for spirited down shift driving. You will see a few more usable ponys too.
After that you are looking at more serious changes, a manifold would be good next. Head work is where the real thought needs to go into things. You will need to look at cams too so that the most can be made of the money you spend. A ported head no matter how well it is done will not work well on its own. It will work, but you need other things to compliment it. Another thing to remember is, the more power you get, the further up the rev range it will be, this will be at the expence of low end torque. There are ways to combat this, but it is a general rule. Not a problem if you spend most of your time above 4000rpm, but it is if you spend time in traffic.
You would now be at the stage where the manufacture's specs are a long way off and you need to look at changing the mapping to get the most out of things. Things can quickly spiral out of control..........
Then there are changes in capacity.
PMed
Unless they have been done to your knowledge, get your injectors cleaned. Make sure your engine is running well and is healthy. There is no point in tuning a rattley worn out turd of a motor.
My personal suggestion would be, a chip (speedtouch), BBTB, and a lightened flywheel, as a first stage. The throttle and flywheel are future proof, as in they will continue to work with any further mods that you do, as will the chip be to a certain extent. You will see a considerable change in the charcter of the engine, much quicker throttle responce, and acceleration in the lower gears. The time it takes the engine to rev down will be less, making it nicer for spirited down shift driving. You will see a few more usable ponys too.
After that you are looking at more serious changes, a manifold would be good next. Head work is where the real thought needs to go into things. You will need to look at cams too so that the most can be made of the money you spend. A ported head no matter how well it is done will not work well on its own. It will work, but you need other things to compliment it. Another thing to remember is, the more power you get, the further up the rev range it will be, this will be at the expence of low end torque. There are ways to combat this, but it is a general rule. Not a problem if you spend most of your time above 4000rpm, but it is if you spend time in traffic.
You would now be at the stage where the manufacture's specs are a long way off and you need to look at changing the mapping to get the most out of things. Things can quickly spiral out of control..........
Then there are changes in capacity.
PMed
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