The E30 without cat (we say VFL in germany. VFL -> Vor Facelift = Before Facelift) has much higher compression (it's not just the fault from the cat, that the older M20B25 is faster) it is way faster under 3000rpm, but the cat versions (NFL -> Nach Facelift = After Facelift) use shorter differential ratios, to compensate that (they try it) Example for the E30 320 320 (125hp) without cat -> First gear 60km/h 320 (129hp) with cat -> First Gear 45km/h One of my E30 is a 90hp 318 with a carburetor engine (and is damn fast for just a 90hp engine)........it use a 3.91 Differential, like the 325 with cat. The 323i (always no cat, and high compression) use a very long diff ratio (first gear 60, second 105) and does 0-100kmh in 7.2. Here is a List when, which differential was used. wp1016621.server-he.de/fotost/f00023/f00023.htm But the list is for germany, maybe E30 from other countrys got other diffs. Because warmer oxygen = less hp
I dont think that it is to short. The funny thing is, the first gear from the 325i is shorter ! as the first from the 320i. And the second gear from the 320 transmission is shorter. Here is a picture with the transmission ratios. i.postimg.cc/4xL7pYqF/E30-Getriebe-bersetzungen.jpg The thing is, the 320VFL is strong enough for a fist gear that goes until 60km/h, and 60-100 for the second gear is the optimum. The only problem is 0-25 (or anything under 3000rpm) that's where the 320 is slow. There are 3 ways to work around that. a) You can use a shorter diff (but not under 4.10, because under 4.10 are diffs with small case ("168" case, the big ones are the "188", The 168 wear out fast, with a 6Cylinder) it will help a lot. But your engine will use more fuel, and the maximum speed goes down (But that's no Problem, because when we drive our old cars over 180km/h ?) and you must change the gear more often. b) You can use a 325 transmission (if you use the 325 transmission you need the propeller shaft (Kardanwelle in german) from the 325 (the 320 propeller shaft is 1-2cm longer) so your first gear is shorter, and the car is more agressive, but the second is longer, and the 3rd gear is shorter, and more agressive. The Maximum Speed will not change. c) Use smaller tyres and light wheels. 205/50/15 with the classic BMW "Kreutzspeiche" Wheels are just 14-15kg per wheel ! (a 17" Wheel with tyre is 20-24kg !) wp1016621.server-he.de/fotost/f01404/kreuzspeiche15.jpg 205/50 and your speedometer will always show 5-7km/h more as in reality, but the acceleration is better. 205/55 is the default for the Kreutzspeiche. Here is a link, where you can calculate how many km/h each gear make, with different stuff. www.m-forum.de/kalkulator/getriebe/ Example Photo. 205/50/15, 325 Transmission, 4.10 Diff postimg.cc/FYZfkKL0 Here some tips. Small Tyres = More acceleration. There is a huge difference between 205 and 225 ! Limited Slip DIfferential (More dangerous when it's raining !) = Better Traction -> Better acceleration. Sharp Camshaft -> More Maximum HP. It will take hp and acceleration under 3000, and give more above 4000. The Point where your engine got his maximum torque (vfl -> 4000) will go up to arround 5000, so you get more hp, but you lose torque at low rpm, and the engine idle at 0rpm gets rough ! Use a OEM Exhaust with Sport Blends ! A non tuned M20 is optimized for the OEM Exhaust. If you got a Sport Exhaust, throw it out. The Sport (bigger pippes in the middle section) exhaust steal just power under 3000rpm ! Put a OEM Exhaust under your E30, and weld some big fake pippes at the end. Sound is loud, and beautiful (because you can still hear the engine good. With a real Sport Exhaust, you hear to 90% just the Exhaust) and your car is more agressive under 3000. Lower your car ! (60/40 or 60/60) Lower car = less air resistance ! Always try drive with 25-35L Petrol ! If the end from your car is to light, the car reacts slower to Gas Pedal changes. Especially when you drive with 60km/h and push the pedal full down (because it takes time for the back part from you car, to sink down) Chip your engine ! (but search for a serious and experienced chip creator for the M20, who knows what he does !) A Chip can change the behavior (example: how many gasoline & oxygen for lets say 30° Celsius) from your engine and you can set the Rev Limiter to 7000 ! Just the rev limiter to 7000, will help a lot. Use the OEM Air Filters ! No Sport Air Filters. These are totaly useless for a normal M20 Engine.
