Max mph for a stock E21

[Rushfan1]

Just curious, what is the maximum speed for a stock 5 speed E21 with the 1.8 L. M10?

[Somjuan]

I think you’ll run into the nose coming up on you around 105 mph. If you have the ‘is’ air dam it should be better. But theoretical max speed depends on final drive, tire size, and which transmission you have.

[amarino]

Here is a website to play with different wheel/tire, transmission, and diff ratios: http://www.kabamus.com/garage/gears.html

Theoretical best case scenario with stock 185/70R13 wheels and tires, 5-speed overdrive at .805, and 3.64 diff you would hit redline on the tach right before 6500rpm at ~150mph.
More likely you have a 3.91 diff and would redline at ~140mph.

But of course you tell the officer that you were only doing 85 as thats what the speedo goes to

[dreiermann]

My memory may be a bit fuzzy on this, but the one time I had my previous 1977 320i (all stock) floored for a couple of minutes it eventually got up to a bit over 100. Maybe 110? I was heading west in western Kansas so I might have had a bit of a headwind. That that was 33 years ago too, so the details are fading away.

[okieflats]

I have a Car and Driver magazine that has the road test and stats like that. See if I can find it.

[okieflats]

All I have is the 1979 Issue. It says for the 2 liter 4 speed the top speed was 109mph. That's "observed" meaning they tested it.

[okieflats]

Here's the answer, 1980 1.8 liter 5 speed 105 mph, same source Car and Driver magazine, top speed as tested.

Specifications
ENGINE (1980-'83) Type: SOHC inline-four, iron block and aluminum head Displacement: 1,766cc Bore x stroke: 89mm x 71mm Compression ratio: 8.81:1 Horsepower @ RPM: 101 @ 5,800 RPM Torque @ RPM: 100 @ 4,500 RPM Main bearings: 5 Fuel system: Bosch K-Jetronic mechanical fuel injection


TRANSMISSION Type: Getrag 245/2 five-speed manual transmission, fully synchronized


STEERING Type: Rack-and-pinion


BRAKES Type: Hydraulic, vacuum-assist Front: 10.0-inch disc Rear: 9.8-inch drum


WEIGHTS AND MEASURES Wheelbase: 100.9 inches Overall length: 177.5 inches Overall width: 63.4 inches Overall height: 54.3 inches Curb weight: 2,435 pounds


PERFORMANCE 0-60: 9.8 seconds 1/4-mile: 17.1 seconds @ 79 MPH Top speed: 105 MPH


Source: Car and Driver, March 1980

[Rushfan1]

Here's the answer, 1980 1.8 liter 5 speed 105 mph, same source Car and Driver magazine, top speed as tested.

Specifications
ENGINE (1980-'83) Type: SOHC inline-four, iron block and aluminum head Displacement: 1,766cc Bore x stroke: 89mm x 71mm Compression ratio: 8.81:1 Horsepower @ RPM: 101 @ 5,800 RPM Torque @ RPM: 100 @ 4,500 RPM Main bearings: 5 Fuel system: Bosch K-Jetronic mechanical fuel injection


TRANSMISSION Type: Getrag 245/2 five-speed manual transmission, fully synchronized


STEERING Type: Rack-and-pinion


BRAKES Type: Hydraulic, vacuum-assist Front: 10.0-inch disc Rear: 9.8-inch drum


WEIGHTS AND MEASURES Wheelbase: 100.9 inches Overall length: 177.5 inches Overall width: 63.4 inches Overall height: 54.3 inches Curb weight: 2,435 pounds


PERFORMANCE 0-60: 9.8 seconds 1/4-mile: 17.1 seconds @ 79 MPH Top speed: 105 MPH


Source: Car and Driver, March 1980

Thanks for the nice consolidated information!

[autox320]

I have to say even with a modded 1.8L. Milled head to up compression close to 9.5 and 286/288 cams It struggled to get 120mph in 5th. That was until put in a custom LSD 427 rearend. Then could hit over 120mph in 5th in shorter distance.

Our new rig I've not honestly checked since no speedo. I suspect it gets into 130mph in short order. You have to remember over 100mph you are trying to "fly a brick"
Asking my buddy if has any track logs for max mph on the straights.

[OLD MAN]

I have to say even with a modded 1.8L. Milled head to up compression close to 9.5 and 286/288 cams It struggled to get 120mph in 5th. That was until put in a custom LSD 427 rearend. Then could hit over 120mph in 5th in shorter distance.

Our new rig I've not honestly checked since no speedo. I suspect it gets into 130mph in short order. You have to remember over 100mph you are trying to "fly a brick"
Asking my buddy if has any track logs for max mph on the straights.

Top speed for our car on the dyno - no wind involved - was 123.xx. in fourth, that is with a 180hp at the wheels M20, 3.91 LSD and 225/45-15s. Ran the engine to 7,600rpm.

https://www.youtube.com/watch?v=t3HX-PfZ-mA

4-10-15 dyno pulls.jpg


So without a lot of power and 3.45 gears, I think getting an E21 over 120mph will take LOTS of power and an engine that can live over 7,500 rpm.

[epmedia]

30, 60, 90, 120 with the 4spd, 3.64, peppy 2.0, all odds rooting for you.

[epmedia]

I have to say even with a modded 1.8L. Milled head to up compression close to 9.5 and 286/288 cams It struggled to get 120mph in 5th. That was until put in a custom LSD 427 rearend. Then could hit over 120mph in 5th in shorter distance.

Our new rig I've not honestly checked since no speedo. I suspect it gets into 130mph in short order. You have to remember over 100mph you are trying to "fly a brick"
Asking my buddy if has any track logs for max mph on the straights.

I had a speeding ticket at 83+ whilst getting around a stinky garbage truck in 3rd gear. Had to take foot off pedal before 4th gear to slow down. Speed trap on the Cali I-15.

I'm not proud of breaking the barrier, just had to get far away from that stinky garbage truck... eek.

[autox320]

Top speed for our car on the dyno - no wind involved - was 123.xx. in fourth, that is with a 180hp at the wheels M20, 3.91 LSD and 225/45-15s. Ran the engine to 7,600rpm.

https://www.youtube.com/watch?v=t3HX-PfZ-mA

4-10-15 dyno pulls.jpg


So without a lot of power and 3.45 gears, I think getting an E21 over 120mph will take LOTS of power and an engine that can live over 7,500 rpm.

Nice I've seen that vid when you first made it. Car engine sounds sick and seems to pull right to redline. I envy a 6 done right with carb. Honestly really pondered your intake and holley 4bbl setup a LOT. Gearing gives leverage to overcome some of the horrible brick wind profile at speed. Yet I can say I've had mine over 120mph on the "street". Not sure on track what it hits unless my buddy can find the actual log files.

Then again if he does I keep in mind front straight at VIR is 3000 ft long and has a serious bend in it. At over 100mph it looks like a "kink" but if don't grip the wheel the car shifts over going through it. Back straight is 4000 ft long but all UP hill except the brake zone. It looks flat unless see a pic from oak tree turn how uphill it really is. Sticky 225/45/15 rubber as well makes for interesting engine load at high speed. Another factor to overcome is "gription" lol

True guys could just run a gearing calculator thats what I initially do. But in real world you need some hp to overcome drag over 100mph with the brick.

With our setup at 7500rpm top speed on the calc says 148mph. I've not seen that but know it's been in 130's before.

[OLD MAN]

Nice I've seen that vid when you first made it. Car engine sounds sick and seems to pull right to redline. I envy a 6 done right with carb. Honestly really pondered your intake and holley 4bbl setup a LOT.

Thanks

I have pondered our intake / carb setup for over 10 years now - LOL.

Really thinking of getting a Holley 570cfm street avenger carb for my 65 chevelle wagon and giving it a test on the M20. If I like it then get a 570 or bigger holley brawler carb. ? ?

Bigger is better right? Thinking I need bigger because the holley 390 nascar carb flows around 530 cfm or so and at wide open throttle the vacuum never drops below 6in. So I am thinking the engine wants way more air/fuel.

[autox320]

Thanks

I have pondered our intake / carb setup for over 10 years now - LOL.

Really thinking of getting a Holley 570cfm street avenger carb for my 65 chevelle wagon and giving it a test on the M20. If I like it then get a 570 or bigger holley brawler carb. ? ?

Bigger is better right? Thinking I need bigger because the holley 390 nascar carb flows around 530 cfm or so and at wide open throttle the vacuum never drops below 6in. So I am thinking the engine wants way more air/fuel.

Have a AFR meter? When on the dyno was AFR on the pic graph accurate? Reason I ask is I'd run as rich as 12.5 AFR at WOT. Can you jet any richer and adjust for keeping midrange without over fueling? This is the area I kept trial and error on the weber 38. There was a break point where more jet finally stopped making power. When it was in the 13's it felt great until added more on top it kept pulling harder till 12.5.

Carb ratings vary by start point. Holley and Weber vary these numbers same for some other model carbs even in same branding. Supposedly the weber 38 is a 390cfm carb. I've no idea if any of my sanding and profiling raised the number, I doubt it. Profiling the auxiliary venturi's "booster" made a nice difference to get onto the mains. Ultimately it's up to the mains and carb cfm though.

Yeah know I'd have to hook up my vac gauge and see what ours pulls at WOT. It's said if over 1.5" that the carb isn't big enough. But like say sometimes that's not completely true and just a guideline. There are carb setups that make more power than others and still pull over 1" vacuum at WOT. Damn it man your making me curious. I'll have to break back out the vacuum gauge next time I take a drive

Another ballpark figure is 2.5xhp to guesstimate cfm.

[elin.alexandrov]

I've pushed my 316 M10B16 with the stock Solex 32/32 DIDTA carb up to 160 km/h or ~100mph on LPG. That's with the stock 4.10 final drive and 5 speed overdrive tranny. It felt scary at that speed and now I'm wondering how it will feel with the M30B30 swap and 3.45 final drive. Theoretically 155mph should be reached at the rev limited 6400 rpm. I've got my hands on an aftermarket Vestatec airdam so hopefully that would prevent the front end from pointing towards the Lord.

Sent from my ONEPLUS A3003 using Tapatalk

[autox320]

I've pushed my 316 M10B16 with the stock Solex 32/32 DIDTA carb up to 160 km/h or ~100mph on LPG. That's with the stock 4.10 final drive and 5 speed overdrive tranny. It felt scary at that speed and now I'm wondering how it will feel with the M30B30 swap and 3.45 final drive. Theoretically 155mph should be reached at the rev limited 6400 rpm. I've got my hands on an aftermarket Vestatec airdam so hopefully that would prevent the front end from pointing towards the Lord.

Sent from my ONEPLUS A3003 using Tapatalk

Instability is due to suspension design and inadequate tire size IMO. Ours is stable but very far from "stock". I'd not want to be in a factory car 150mph no way would be sketch as frig.

[goinstrong]

I had my stock 1981 (except H and R springs, Bilsteins and 15” Alpinas) out at Pacific Raceways. It was the 3 lap parade for the Car Control Clinic. A guy cut in ahead of us so we were delayed getting on the track. The guy ahead of me was in a turbocharged E46. On the straight I tried to stay with him and had it floored in 5th gear as we sped up to catch the parade. Speedo was pinned so no idea how fast we were going. After we finished I asked the guy how fast we were going on that first straightaway. He said 105. Impressive because my E21 at the time had 227,000 on it! Factory max speed after all those miles. FYI: the E46 would go ahead on the straights, but I would catch up to him in the curves!


Sent from my iPhone using Tapatalk

[okieflats]

.... It felt scary at that speed .....

were you driving an uneven road with dips and humps?

Weak worn shocks are really bad because they let the car, especially the rear, lift when going over bumps or dips. So if you have old shocks you';d benefit from new ones especially with strong damping on the rebound.

[autox320]

Thanks

I have pondered our intake / carb setup for over 10 years now - LOL.

Really thinking of getting a Holley 570cfm street avenger carb for my 65 chevelle wagon and giving it a test on the M20. If I like it then get a 570 or bigger holley brawler carb. ? ?

Bigger is better right? Thinking I need bigger because the holley 390 nascar carb flows around 530 cfm or so and at wide open throttle the vacuum never drops below 6in. So I am thinking the engine wants way more air/fuel.

Have a AFR meter? When on the dyno was AFR on the pic graph accurate? Reason I ask is I'd run as rich as 12.5 AFR at WOT. Can you jet any richer and adjust for keeping midrange without over fueling? This is the area I kept trial and error on the weber 38. There was a break point where more jet finally stopped making power. When it was in the 13's it felt great until added more on top it kept pulling harder till 12.5.

Carb ratings vary by start point. Holley and Weber vary these numbers same for some other model carbs even in same branding. Supposedly the weber 38 is a 390cfm carb. I've no idea if any of my sanding and profiling raised the number, I doubt it. Profiling the auxiliary venturi's "booster" made a nice difference to get onto the mains. Ultimately it's up to the mains and carb cfm though.

Yeah know I'd have to hook up my vac gauge and see what ours pulls at WOT. It's said if over 1.5" that the carb isn't big enough. But like say sometimes that's not completely true and just a guideline. There are carb setups that make more power than others and still pull over 1" vacuum at WOT. Damn it man your making me curious. I'll have to break back out the vacuum gauge next time I take a drive

Another ballpark figure is 2.5xhp to guesstimate cfm.

fyi;

Today I thought of this post and checked my carb with a vacuum gauge. Left it on and went for a drive with it mounted in the cockpit. Under WOT my setup with the 2.3L fueled by 38/38 needle hits the zero on the gauge. I did a few pulls and yup definitely vacuum drops below 1" and touches zero. I put a dab of marker paint of the edge of the gauge at zero since it's easier to see when under throttle. Needle lines up with the paint.