Here's a lot of info to digest! I put up some basic power levels to be expected with various amounts of work, then old links to threads with more info. I may get around to adding dyno plots (and I welcome your Dynojet run files for my stash!).
This is about engines, but to have a fast N/A car, you need to “add lightness” and close/short gearing to give you mechanical advantage. Getting rid of that 3.31:1 diff. can help more than you think! Smaller wheels and tires are lighter in addition to giving you shorter gearing.
This was thrown together quickly, but you get the idea.
The first step assumes you already have a good Stage 0 of no vacuum leaks, good plugs, wires, cap/rotor, sensors work, throttle's clean, etc..
Cheap N/A power step 1 (go from stock 70-90whp/90-110wtrq and 18-20s+ 1/4 miles to 90-120whp/120-140wtrq and 16-18s 1/4 miles):
1. Tighten your valves on your current cam (.010-.014")! If using a D, K or H, you'll want to keep the clearances closer to .016" or .018" for a better/smoother idle and off idle perf. because they have higher duration and overlap than all the other factory cams. The tighter the valves, the minutely larger/higher duration the cam becomes at the expense of worse idle and emissions. On most of the factory cams, they'll still idle fine. The D, K and H can be rough with tighter clearances and won't be ideal if you have stock compression and EFI.
2. Clean your fuel system/injectors and soak your pistons to get rid of carbon build-up, especially in the rings to restore lost compression (Seafoam, Marvel Mystery oil, other top end cleaners, etc.). Have your injectors cleaned, or use a Techron/similar fuel system cleaner in your tank.
3. Raise the ignition timing if LH2.2 or earlier. You won't want to do too much if running regular fuel and using the smaller or original cam, but you can get away with more if running the larger cams that have more duration such as the D, K and H as they reduce the Dynamic Compression Ratio (DCR) more.
4. If running an M or T cam (T is better, BTW!), retard the cam timing 2-4 degrees if you have an adjustable gear. Make sure it's legit and the timing marks are accurate (unlike some of IPD's early drilled gears). If you can afford a cam swap, anything is an upgrade other than the L.
5. The D, K or H cam are a little sluggish off idle on a stock engine without custom spark and/or fuel tuning, but they'll all work fine and make ok power from 2k rpm on up, with more than any of the others above 3-3.5k rpm or so. The K is the best all around factory cam. The H idles worse and may or may not make more peak power in some setups. With these cams, if you have an adjustable cam gear, try advancing it 2-4 degrees to improve your low end torque in daily use.
6: Remove the hot air intake flap from the airbox and re-route the pre-heat tube to fresh air at the front of the car (in the bottom spoiler, or the passenger side of the radiator support).
7. You can modify the exhaust. Ideally, you'd upgrade to at least 2.25" piping such as the original style turbo exhaust with the single muffler in the back. Not much power to be gained here, but it'll sound better and make a little bit of difference just like everything else.
"Cheap" N/A power step 2 (110-140whp/130-150wtrq and 15-16s 1/4 miles):
Basically, SHAVE THE HEAD .040"/1mm or more depending on cam choice, get your head surface closer to the piston tops and use a minimum of a B, A, V, VX, D, K or H cam. Ideally you'd be using something along the lines of an IPD Turbo cam, ENEM V15NA (likely almost as much peak power as the K and H cams, but a wider powerband with more torque), V16NA or similar offerings from other vendors. A thinner headgasket is your friend allowing a .030-.040" maximum piston to head clearance which improves combustion efficiency and helps prevent detonation. If your bottom end is in good shape and you don't want to rev over 6k rpm, many have gone even tighter than that (possibly some as low as .020" clearance, but you're pushing your luck!). You'll want your 2.25" or 2.5" exhaust starting at the factory 2-1 merge in the downpipe and continuing back (build or buy a larger collector so it doesn't neck down to stock diameter at all). You'll want/need to look into adjusting your ignition timing and likely your fueling to dial in a better powerband and keep detonation at bay. Premium fuel may be required depending on your choices. *Factory ignition timing can be too much advance in some circumstances.* This engine can still pull very strongly from idle and have more power than stock starting at very low rpm (2000rpm?). It can be very efficient and great for daily use and keeping up with or even beating modern traffic depending on the rest of the setup. Works fine with lazy, 4spd autos.
Not cheap N/A power step 3 (135-185whp/140-170wtrq):
Recommended minimum of the K-jet intake manifold for the larger diameter runners for best results, but 45mm/48mm individual throttle bodies or carbs will do even better. You can do over 140whp on the stock B230F style manifold, but it's basically at its peak and holding you back. You will want a larger diameter 2-1 downpipe for best results, but stock sized can still do over 140whp with the larger 2-1 merge collector for it that mates with your larger exhaust. K/H cams are near their limits and you ideally want something more modern with at least 12mm of lift, such as the Enem K13 or larger (Enem C2 with 14mm of lift if your head setup has room and the springs for it?). Think about having port work done to improve head flow, and/or use the 405/531 heads (neither are required for 135whp, but, the better the flow; the better the overall result). You can go to a properly sized 4-2-1 header, but it's not required. - The General Leif has over 165whp still with a mildly ported, factory exhaust manifold. You will need the ability to tune your fuel and spark. Either LH2.4/3.1 with an Ostrich or custom chips, carbs, or stand-alone engine management. You will likely want at least .040"-.080" off your head or even more depending on your cam, piston-head clearance, head and combustion chamber volume. A fresh bottom end with good ring seal is your friend here, but it's not required. You do NOT NEED larger than stock valves but they might help if the head is set up right for them. The General Leif is at/over 165whp with stock diameter valves. Depending on cam choice and everything else, you may be able to accelerate fine from an idle, but it might not like full throttle until over 2000-3000rpm without special tuning (individual throttles can help, but aren't required).
Expensive N/A power step 4 (175-220+whp and 150-180wtrq):
Bigger cam, 2.5-3mm off a well ported head with chamber mods for unshrouding, etc., custom intake manifold or 48-50mm carbs/ITBs, custom 4-2-1 header with 44.5mm primaries, 51mm secondaries, etc.. Custom EFI and mapping, etc.. Better valve springs to deal with the quick opening and closing of the valves with the high 13-15mm lift cams and higher durations, etc.. Bigger valves aren't required but likely will be a better match at this point. 2.5L+ optional.
SERIOUS N/A power step 5 (220-270whp at higher rpm and similar peak torque):
MORE. Like, 15+mm camshafts, bigger valves, EVO or very worked over heads, 8000+rpm, worked over 16V heads if you want, 2.5L+, etc...
LH TUNING:
I attached a zipped folder with bin/xdf files and the checksum tool for TunerPro if running LH2.4 or LH3.1 and want to tune your own! You'll need need TunerPro or the BOSCH LH 2.4 EDITOR. https://www.turbobricks.com/index.php?threads/fuel-spark-tuning-for-lh-2-4-ezk-with-tunerpro.227153/ If you don't have an Ostrich, you can get a chip burner online and do it that way instead. I included a tweaked 951 bin file and notes that I'm running on my car with a slightly shaved 530 head, .036" headgasket, 16V White-Top fuel injectors, H cam, opened airbox and a full exhaust if you want to try it out.
10/24: See dead links in a post just below.
This is about engines, but to have a fast N/A car, you need to “add lightness” and close/short gearing to give you mechanical advantage. Getting rid of that 3.31:1 diff. can help more than you think! Smaller wheels and tires are lighter in addition to giving you shorter gearing.
This was thrown together quickly, but you get the idea.
The first step assumes you already have a good Stage 0 of no vacuum leaks, good plugs, wires, cap/rotor, sensors work, throttle's clean, etc..
Cheap N/A power step 1 (go from stock 70-90whp/90-110wtrq and 18-20s+ 1/4 miles to 90-120whp/120-140wtrq and 16-18s 1/4 miles): 1. Tighten your valves on your current cam (.010-.014")! If using a D, K or H, you'll want to keep the clearances closer to .016" or .018" for a better/smoother idle and off idle perf. because they have higher duration and overlap than all the other factory cams. The tighter the valves, the minutely larger/higher duration the cam becomes at the expense of worse idle and emissions. On most of the factory cams, they'll still idle fine. The D, K and H can be rough with tighter clearances and won't be ideal if you have stock compression and EFI.
2. Clean your fuel system/injectors and soak your pistons to get rid of carbon build-up, especially in the rings to restore lost compression (Seafoam, Marvel Mystery oil, other top end cleaners, etc.). Have your injectors cleaned, or use a Techron/similar fuel system cleaner in your tank.
3. Raise the ignition timing if LH2.2 or earlier. You won't want to do too much if running regular fuel and using the smaller or original cam, but you can get away with more if running the larger cams that have more duration such as the D, K and H as they reduce the Dynamic Compression Ratio (DCR) more.
4. If running an M or T cam (T is better, BTW!), retard the cam timing 2-4 degrees if you have an adjustable gear. Make sure it's legit and the timing marks are accurate (unlike some of IPD's early drilled gears). If you can afford a cam swap, anything is an upgrade other than the L.
5. The D, K or H cam are a little sluggish off idle on a stock engine without custom spark and/or fuel tuning, but they'll all work fine and make ok power from 2k rpm on up, with more than any of the others above 3-3.5k rpm or so. The K is the best all around factory cam. The H idles worse and may or may not make more peak power in some setups. With these cams, if you have an adjustable cam gear, try advancing it 2-4 degrees to improve your low end torque in daily use.
6: Remove the hot air intake flap from the airbox and re-route the pre-heat tube to fresh air at the front of the car (in the bottom spoiler, or the passenger side of the radiator support).
7. You can modify the exhaust. Ideally, you'd upgrade to at least 2.25" piping such as the original style turbo exhaust with the single muffler in the back. Not much power to be gained here, but it'll sound better and make a little bit of difference just like everything else.
"Cheap" N/A power step 2 (110-140whp/130-150wtrq and 15-16s 1/4 miles):Basically, SHAVE THE HEAD .040"/1mm or more depending on cam choice, get your head surface closer to the piston tops and use a minimum of a B, A, V, VX, D, K or H cam. Ideally you'd be using something along the lines of an IPD Turbo cam, ENEM V15NA (likely almost as much peak power as the K and H cams, but a wider powerband with more torque), V16NA or similar offerings from other vendors. A thinner headgasket is your friend allowing a .030-.040" maximum piston to head clearance which improves combustion efficiency and helps prevent detonation. If your bottom end is in good shape and you don't want to rev over 6k rpm, many have gone even tighter than that (possibly some as low as .020" clearance, but you're pushing your luck!). You'll want your 2.25" or 2.5" exhaust starting at the factory 2-1 merge in the downpipe and continuing back (build or buy a larger collector so it doesn't neck down to stock diameter at all). You'll want/need to look into adjusting your ignition timing and likely your fueling to dial in a better powerband and keep detonation at bay. Premium fuel may be required depending on your choices. *Factory ignition timing can be too much advance in some circumstances.* This engine can still pull very strongly from idle and have more power than stock starting at very low rpm (2000rpm?). It can be very efficient and great for daily use and keeping up with or even beating modern traffic depending on the rest of the setup. Works fine with lazy, 4spd autos.
Not cheap N/A power step 3 (135-185whp/140-170wtrq):Recommended minimum of the K-jet intake manifold for the larger diameter runners for best results, but 45mm/48mm individual throttle bodies or carbs will do even better. You can do over 140whp on the stock B230F style manifold, but it's basically at its peak and holding you back. You will want a larger diameter 2-1 downpipe for best results, but stock sized can still do over 140whp with the larger 2-1 merge collector for it that mates with your larger exhaust. K/H cams are near their limits and you ideally want something more modern with at least 12mm of lift, such as the Enem K13 or larger (Enem C2 with 14mm of lift if your head setup has room and the springs for it?). Think about having port work done to improve head flow, and/or use the 405/531 heads (neither are required for 135whp, but, the better the flow; the better the overall result). You can go to a properly sized 4-2-1 header, but it's not required. - The General Leif has over 165whp still with a mildly ported, factory exhaust manifold. You will need the ability to tune your fuel and spark. Either LH2.4/3.1 with an Ostrich or custom chips, carbs, or stand-alone engine management. You will likely want at least .040"-.080" off your head or even more depending on your cam, piston-head clearance, head and combustion chamber volume. A fresh bottom end with good ring seal is your friend here, but it's not required. You do NOT NEED larger than stock valves but they might help if the head is set up right for them. The General Leif is at/over 165whp with stock diameter valves. Depending on cam choice and everything else, you may be able to accelerate fine from an idle, but it might not like full throttle until over 2000-3000rpm without special tuning (individual throttles can help, but aren't required).
Expensive N/A power step 4 (175-220+whp and 150-180wtrq):Bigger cam, 2.5-3mm off a well ported head with chamber mods for unshrouding, etc., custom intake manifold or 48-50mm carbs/ITBs, custom 4-2-1 header with 44.5mm primaries, 51mm secondaries, etc.. Custom EFI and mapping, etc.. Better valve springs to deal with the quick opening and closing of the valves with the high 13-15mm lift cams and higher durations, etc.. Bigger valves aren't required but likely will be a better match at this point. 2.5L+ optional.
SERIOUS N/A power step 5 (220-270whp at higher rpm and similar peak torque):MORE. Like, 15+mm camshafts, bigger valves, EVO or very worked over heads, 8000+rpm, worked over 16V heads if you want, 2.5L+, etc...
LH TUNING:
I attached a zipped folder with bin/xdf files and the checksum tool for TunerPro if running LH2.4 or LH3.1 and want to tune your own! You'll need need TunerPro or the BOSCH LH 2.4 EDITOR. https://www.turbobricks.com/index.php?threads/fuel-spark-tuning-for-lh-2-4-ezk-with-tunerpro.227153/ If you don't have an Ostrich, you can get a chip burner online and do it that way instead. I included a tweaked 951 bin file and notes that I'm running on my car with a slightly shaved 530 head, .036" headgasket, 16V White-Top fuel injectors, H cam, opened airbox and a full exhaust if you want to try it out.
10/24: See dead links in a post just below.
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