Author Topic: Peak Torque RPM for 1.6 NA? (Read 12160 times)

Northboundtrain · « **on:** January 25, 2007, 12:01:14 pm »

Can anyone tell me at what RPM the 1.6 makes peak torque? I'm installing a new engine (and maybe tranny) in my '91 Jetta. The current tranny has a 0.89 5th gear and a 3.94 final drive. By my calculations, with 22" tires, I'm doing about 3,750 rpm at 70 mph, which seems too high for optimal fuel economy. I have an older tranny that I think has a 0.71 5th and a 3.89 final drive. That translates to about 2,950 rpm at 70 mph, which seems better. But would even lower rpms get better torque from the engine and thus better efficiency (that's why I'd like to know the peak torque rpm)? If so, has anyone heard of modifying the final drive ratio?

Information, opinions, suggestions greatly appreciated.

Thanks

SMOKEYDUB · « **Reply #1 on:** January 25, 2007, 01:30:05 pm »

i think peak torque is around 2400

burn_your_money · « **Reply #2 on:** January 25, 2007, 03:14:57 pm »

www.brokevw.com for lots of tranny info

clbanman · « **Reply #3 on:** January 26, 2007, 06:38:15 am »

According to http://www.4crawler.com/Diesel/SAE/vwtdsae.shtml, "The maximum torque is 102 Nm at 2000 rpm." This is in a section on the 1.5/1.6 engine family, so I'm not sure if that is true for the latest versions of the engine. The paper does also mention that "The latest development of the naturally aspirated Diesel engine was concluded in early 1981..."

gldgti · « **Reply #4 on:** January 26, 2007, 02:45:34 pm »

my manual states peak torque in the 1.5 NA is at 3000 rpm, and in the 1.6 is at 2800 rpm.

i can certainly vouch for the figure in the 1.5, thats where all the power begins (what little there is).

the only difference is stroke, so i'd say that thats where it'll be, a bit below 3k.

Northboundtrain · « **Reply #5 on:** January 28, 2007, 09:01:09 am »

Hmmm, some different numbers here. Just out of curiosity, what factors affect peak torque rpm, other than stroke length? Here's an engine with a slightly smaller displacement than the 1.6L, shorter stroke, same number of cylinders, and similar compression ratio. It supposedly makes peak torque at 1,700 rpm.

http://www.perkins.com/cda/files/334142/7/404d-15%20engine%20(pn1818%20-%20mar06).pdf

According to the chart on brokevw.com, The tallest gears available are in the code 6G transmission. If I get this tranny, the flanges are 90 mm. So I would have to get new axles, which is no big deal if they will fit into the existing hubs. I just did a front end job to this car, and I know the wheel bearings are a different size than those on the older A1 generation cars that had the 90 mm flange tranny. Are the hubs a different size too? I guess I could also just swap the inner CV joint if the older axles don't fit the newer hubs. Also, what about the tranny mounts -- A1 tranny going in an A2 chassis?

jtanguay · « **Reply #6 on:** January 28, 2007, 09:25:08 am »

i've always known perkins to be extremely powerful engines... i know a guy who installed one into a mazda truck.. 4 cylinder. he said the body would give first if dragging something really heavy.

flash319 · « **Reply #7 on:** January 29, 2007, 09:37:57 am »

I would say that the peak torque would depend on the pump and turbo setup. The cam would also dictate it but you could move the torque around a bit with the size of turbo and how your pump delivers fuel. I bet if you run a small turbo yor peak torque may be in the low 2 grand area.

burn_your_money · « **Reply #8 on:** January 29, 2007, 03:09:09 pm »

Quote from: "Northboundtrain"

According to the chart on brokevw.com, The tallest gears available are in the code 6G transmission. If I get this tranny, the flanges are 90 mm. So I would have to get new axles, which is no big deal if they will fit into the existing hubs. I just did a front end job to this car, and I know the wheel bearings are a different size than those on the older A1 generation cars that had the 90 mm flange tranny. Are the hubs a different size too? I guess I could also just swap the inner CV joint if the older axles don't fit the newer hubs. Also, what about the tranny mounts -- A1 tranny going in an A2 chassis?

I'm pretty sure that the hubs are the same (all A2 the same, all A1 the same) You can run either 100 or 90mm cvs with any tranny. All you have to do is swap the flanges on the transmission. It's a good idea to change those seals in there anyways.

A1 tranny will not work in a mk2 unless you make a custom mount. A couple of the holes are missing on the casing as you can see here

I want to run a mk1 tranny in my mk2 but I haven't tried anything yet

As far as factors effecting torque, the speed that the air is forced into the engine also is a factor IIRC

Northboundtrain · « **Reply #9 on:** January 29, 2007, 04:56:18 pm »

Well that's good to know -- that a A1/MK1 tranny won't bolt right in to a A2/MK2 chassis. Can anyone recommend the best tranny to get given that I want the tallest gears possible. From the chart on brokevw.com, it looks like there are several options that have an overall (differential multiplied by 5th) ratio of 2.75:1, which is the tallest listed for 100 mm flanges (I'm assuming 100 mm flanges mean A2/MK2).

Thanks again.

bvolks73 · « **Reply #10 on:** January 29, 2007, 06:42:44 pm »

I have an A1 transmission out of an 84 Jetta in my 85 Coupe. For some reason it has the extra holes. I'm not sure of the gear ratios or final drive but they're much higher than in the tranny I took out. I found myself having to downshift to 4th on hills that I got over in 5th with the old tranny.

janb · « **Reply #11 on:** January 29, 2007, 09:21:54 pm »

Quote from: Northboundtrain

...Can anyone recommend the best tranny to get given that I want the tallest gears possible. ...

for my NA's I prefer ASF or ACN (gas trannies), but... I'm concerned about your altitude, as my NA's have to be pretty healthy to comfortably pull 5th in those tall boxes. (at 500-1500ft altitude) The AGS ('86 TD trannie) is my favorite general purpose diesel ratio. I had a 9A close ratio that I changed to a .75 fifth that was as sweet Mountain trannie (3 gears between 35 and 50).

I took my A2 Jetta w/ 1.9 NA w/ ASF to Montana and it was noticably 'challenged' at altitude, climbing passes. Oh, the TDI likes mtns

I'm currently making an A2 GTD, and will probably use the (9A with modified (.75) fifth.)

burn_your_money · « **Reply #12 on:** January 30, 2007, 04:36:47 am »

Quote from: "Northboundtrain"

which is the tallest listed for 100 mm flanges (I'm assuming 100 mm flanges mean A2/MK2).

Dangerous assumption. Most of the mk2s are 90mm, 16Vs for the most part are only 100mm, there are a couple 8vs that were 100mm, but never a diesel (that I know of)

It's been a while since I looked but I think an AGS with a swapped 5th (0.71) would give you the absolute highest gearing in 5th, short of using a 4 speed 4A. I have a 4S and I really enjoy it. I have small winters on my car and am at 2600 at 100kmh (60mph)

Northboundtrain · « **Reply #13 on:** January 30, 2007, 10:23:17 am »

So the ACN will have me spinning 2,950 rpm at 70 mph, which is way better than the current 3,700 that I'm doing at that speed. I'm doing everything I can to get more out of the new engine I'm rebuilding -- ported head, opened up exhaust, giles pump, cold air intake. So I don't think the engine should have trouble with the taller gears.

One thing I don't get: the gasser trannys have taller gears than the diesels. Why?

VWCaddy · « **Reply #14 on:** January 31, 2007, 06:47:07 pm »

Quote from: clbanman

According to http://www.4crawler.com/Diesel/SAE/vwtdsae.shtml, "The maximum torque is 102 Nm at 2000 rpm." This is in a section on the 1.5/1.6 engine family, so I'm not sure if that is true for the latest versions of the engine. The paper does also mention that "The latest development of the naturally aspirated Diesel engine was concluded in early 1981..."

That is for the 1.6TD, the 1.6D is 71 ft,lbs. @ 2500 RPM:
http://www.4crawler.com/Diesel/index.shtml#EngineSpecs

I just got done having a 3.67 final drive installed in my FN transaxle. Gives me around 2600 RPM @ 70 MPH. It did take a bit of the pep out of 5th gear (1.9D engine), but is still very driveable.