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Old 10-27-2004, 09:58 AM   #1
wurlyvalve
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Member#: 73330
Join Date: Oct 2004
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Location: England
Vehicle:
1998 Legacy BH9
Deep Red

Default NA tuning the 1.6

Hi,

I live in England, and as such the turbo Impreza is highly popular - alas, nobody there has a clue how to actually tune the engine (just the turbine). So I wish to seek information and advice on tuning the NA flat four.

I have a 1.6 1994 16V single cam per bank motor. I'm looking to get as much out of it as I can. However, I have a long term interest in building my next sprint car (solo?) with a NA sub 2.0litre engine. If I use a turbo or > 2.0 the race license becomes very tricky. So any information on ultimate tune of the engine would be nice, like which block is strongest, which'll bore out furthest, which crank is strongest, which heads/cams etc etc.

Thanks in advance, I have zero experience with this engine, although have plenty of engine building experience with other mills.

Cheers,
Glen.
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Old 10-27-2004, 05:47 PM   #2
Section 8
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Quote:
Originally Posted by wurlyvalve
Hi,

I live in England, and as such the turbo Impreza is highly popular - alas, nobody there has a clue how to actually tune the engine (just the turbine). So I wish to seek information and advice on tuning the NA flat four.
The "2 liter" turbo block is actually less than 2 liters (ie legal for 2 liter class restrictions). You will want that or at least a 1.8 instead of the 1.6. At a bare minimum you must have the dual port heads if you expect to have any assemblence of parts that will be worth while.

Quote:
Originally Posted by wurlyvalve
I have a 1.6 1994 16V single cam per bank motor. I'm looking to get as much out of it as I can. However, I have a long term interest in building my next sprint car (solo?) with a NA sub 2.0litre engine. If I use a turbo or > 2.0 the race license becomes very tricky. So any information on ultimate tune of the engine would be nice, like which block is strongest, which'll bore out furthest, which crank is strongest, which heads/cams etc etc.
Are you looking to abuse the rules by using a sub two liter block and turning it into something else? You can get a 2.8 liter if your wallet can handle it.

If you obtain a pair of dual port heads, there are a few equal length headers available. You need a set. THere are also a few places that sell cams, you also need those. Depending how far you want to take the engine, an agressive head port, with parts for higher reving, and higher compression could be included.

I would stay away from the 1.6 just because it is to small, and you will have to spend significent dollars to just approach the output of a stock larger engine.

The strongest off the shelf engine will be the EJ22T turbo block. Change the pistons and you have an engine with piston cooling and ridged cylinder bores. THe problem is that it exceeds your 2.0 liter requirement at 2.2 liters.

Custom pistons and rods for any engine will all be roughly the same in price. "custom" parts are the norm, so tweeking current deisgns command little if any charges above the typical part.

You might look into destroking a 2.5 liter block, or a 2.2 to reach your 2.0 requirement. A 2.5 (or the EJ22T would probably be the best bet, phase 1 cranks from a smaller displacement might just fit it) with a short stroke and a sky high red line could be pretty potent. With a higher redline, and intake manifold becomes a necessity as well. You will need to provide your own, as there are no suitabl aftermarket manifolds to choos from.


cheeRS,

Greg
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Old 10-28-2004, 10:49 AM   #3
wurlyvalve
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1998 Legacy BH9
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Default

Excellent, thankyou for that. Nice to get some advise.

I thought the EJ16 and EJ18 were the same motor, barring that the 1.6 had a short stroke crank? Likewise the EJ20 and EJ22 were the same but the 2.0 had a shorter crank? Might be wrong, just thought that to be the case.

No, don't want to abuse the rules. I'm only cheating myself in the end. Would like a short stroke 2.0 so I can wring some high rev power out of the thing. Need about 250 - 300hp to last about 15miles (in total).

But in the short term, so I can get a feel for the engine, I want to have a little play with my 1.6 which resides in my support car.

2.2 turbo is a bit rare in the UK. I think the 22B had it?????? Some Legacy's do too. The 1.6 has dual port heads, I think? As in 2 exhaust ports per bank (each of which look like they are two ports joining next to the exhaust flange).

Intake is no problem, can sort that out when I switch to MegaSquirt. Equal length headers - what sort of lengths work, and what sort of od/id? I'll have a go at fabbing some over winter.

Will the '2.5' cams that Cobb sell (for example) fit into every 'single cam' head? What are my options for cams?

Cheers,
Glen.
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Old 10-28-2004, 12:06 PM   #4
Section 8
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THe EJ22T is the turbo Legacy motor here, and it is different thatn the 22B motor. I don't know anything about the 1.6 or 1.8, but if there are two exhaust hols per head, then you have a proper seat of heads to modify.

The easiest way to change the cam profile will be to have them reground. Several places will regrind cams for you, Webcams (US), Colt cams (Canada) are a couple who have Subaru exeriance. The problem I see with getting a cam for a 2.5 and putting it in your 1.6, even if it fits, is that the lift and duration most likely will not be right for the valve diameter and the ammount of air that the 1.6 will need. I do not know what the relationship is between valve lift, duration and valve diameter. I just know the geometric relation between flow area around the vlave and lift, and I don't think that scaling the larger to the smaller is a valid method to determine it. A company who grinds cams can measure your stock cam, and recommend a grind for you based on what it already does in your engine, and what you want it to do. Of course calling one of the places who sell 2.5 cams would be helpful if they have anything to say about it.

I forgot what the ratio of exhaust production to intake charge is, I will look for it, but I feel the best way to determine your exhaust diameter would be to scale the primary diameter to the exhaust velocity. Using the ratio of the intake charge to exhaust production, find the ammont of exhaust produced, then match the exhaust velocities between the 1.6 and the 2.5 by changing the exhaust diameter to suit the 1.6. Thinking about it a little, you could also just use the ammount of intake charge too. It won't matter because the number will be a ratio, and the intake to intake vs exhaust to exhaust will be the same ratio. Determine the velocity of the intake charge through the primary of a 2.5 header, then use tis velocity and compute the diameter of the pipe needed to obtain this velocity with the intake charge of the 1.6. Remember that you are actually scaling the flow area to affect velocity, and you find the needed diameter from the area that you calculated.

My headers are about 53 inches long with a cross over pipe connecting cylinders that are firing 180 degrees apart approximatly 25.5 inches from the head. Primaries are
1.75 inch in diameter, merge to a 2.5 inch collector and continue 2.5 inches to the tail pipe. It is an exhaust set up for higher RPM and a built motor. I am not yet to the point of "needing" this header, but I would rather have it, and build to it, than to need to replace it later. A very good performer with a basically stock engine to a cammed, with head work engine is 1.625 inch primaries, with a 2.25 inch exhaust.

THis is my header:



Tech Works Engineering (Web Page) built them, and if you wanted a set sized differently, they will more than likely be able to accomidate you. THey coul also give you help with the cam shaft grind (they work with Colt Cams for their own cam shafts).

cheeRS,

Greg
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Old 10-28-2004, 12:10 PM   #5
Section 8
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Oh and I really like the idea about destroking the 2.2 Turbo motor for 2.0L class competition.

The 2.2T's are $1400.00 US the last time I checked.

I want an EZ30 with 6 exhaust ports reallllly bad (they are single port heads).

cheeRS,

Greg
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