What ratios to choose? Standard Mi16 engine.

[B1ack_Mi16 67]

Engine: 1.9 Mi16 on DFW 147bhp 3 row management, but with 10.4:1 pistons from D6C.

 

Orginal gearbox on is probably standard as attached to the 1.9 8v 105bhp Gentry engine?

(I found revs in 5th to be too high after I did some test driving a couple of weeks ago).

 

I also have an Mi16 box frmo my good old 405 to take parts from and I have these data on the ratios etc:

So the specs of the boxes and two hybrid options I've looked at.

 

Hybrid 1 is basicly the Gentry box with 3, 4 and 5th gear from the Mi16 box.

Hybrid 2 is the Gentry box with only 5th gear from Mi16.  Do you think the big difference between 4th and 5th in this setup is too eccessive? I suppose the hybrid 1 solution at least will even out the spacing between the gears a tad better.

 

Both alternatives will at least give quite improvement in cruising revs in 5th which is the main purpose.

 

Thanks for any input/experience.

 

 

 

 

 

 

Edited August 16, 2019 by B1ack_Mi16

[petert 585]

The Gentry box is 3.94 cwp and 0.865 5th, yes?

 

The Mi16 box is 4.43 cwp and 0.76 5th, yes?

 

Thus

3.94 x 0.865 = 3.41:1

 

4.43 x 0.76 = 3.37:1

 

That is a difference of only 1.2%. How can you say it revs too high? Nobody ever said an Mi16 revs too high.

 

Running the 0.76 5th on the Gentry box is a disaster. The gap is huge. It would be great for crossing the desert but nothing else. As you can see from your graph, the 205 and 405 overall ratios for 3rd, 4th and 5th are nearly identical. If I was lazy, I would just keep the 205 box. If I was keen, I'd fit the 2.92 1st from the Mi16 box to the the 205 box.

Edited August 16, 2019 by petert

[jackherer 543]

I agree with Peter, the MI16 box doesn't rev too high.

 

Presumably this is a 'fun' car and not a daily driver that does high mileage? If so keep the revs up or it'll be boring to drive.

[B1ack_Mi16 67]

I suppose it is due to me beeing used to driving 407 and 5008 HDi's and I didn't like the high revs in the 205 when running at motorway speeds. Suppose I'm getting old, that's probably it.

 

The 1 and 2nd gear are the same between the two boxes actually. 

[B1ack_Mi16 67]

Thing is the difference in 5th is minor between the two boxes in standard form.

Maybe I shall just keep the gentry box then and add the Mi16 5th gear. If it proves too sloppy in real life I can change it back anyway without removing the gearbox from the car.

[petert 585]

I did it once. Never again. The gap is huge.

[SRDT 175]

14 hours ago, B1ack_Mi16 said:

Orginal gearbox on is probably standard as attached to the 1.9 8v 105bhp Gentry engine?

The Gentry gearbox looks specific to this model, others XU9J1 use the short "T" ratios like the GTI and it looks like your gearbox is one of those.

The real Gentry gearbox is fitted with the "N" ratios, same as the Mi16 ratios except for the 1st gear as the Mi16 use the long GTI one.

 

With the 16x63 final ratio and the Mi16 gear ratios your hybrid 1 is almost a real Gentry gearbox, you can also find this (16x63 + "N" ratios) on the mk2 309 1.6 bdw.

[welshpug 1,655]

ear defenders and oem engine mounts, and dynamat

[B1ack_Mi16 67]

4 hours ago, SRDT said:

The Gentry gearbox looks specific to this model, others XU9J1 use the short "T" ratios like the GTI and it looks like your gearbox is one of those.

 The real Gentry gearbox is fitted with the "N" ratios, same as the Mi16 ratios except for the 1st gear as the Mi16 use the long GTI one.

 

With the 16x63 final ratio and the Mi16 gear ratios your hybrid 1 is almost a real Gentry gearbox, you can also find this (16x63 + "N" ratios) on the mk2 309 1.6 bdw.

 

Ok, thanks for some input. I actually think the Hybrid 1 option might not be too bad. It's not a trackday car anyway, just to drive and buy icecream with the kids, and listening to good old 90's music

[SRDT 175]

There is a gearbox that is close to the Mi16 one but with a 6th gear:

 

The thing is that it's not the BE3/6 it's a new design and no one tried it yet.

 

 

[B1ack_Mi16 67]

I get it.. well I won't be putting too much effort into this.

 

But I found a 405 1.9 D box in the garage, it had a 5th between the original and the Mi16 one. So I think I will go for keeping 1-4 and FD from the orginal box and just changing 5th gear to the 405 1.9 D one.

Ratio on that was (44/35) 0.795.

 

[petert 585]

Now you're talking. I use to run the following in my daily driver Mi16. The lower 1st help saved the clutch in Sydney traffic.

3.25

1.85

1.36

1.069

0.81 (from an Mi16x4)

4.43 cwp

[B1ack_Mi16 67]

Yes, it will drop revs from 7200rpm to 5300rpm when shifting 4th to 5th opposed to 5100rpm with the Mi16 5th gear in place.

Anyway I can just change the 5th later on also without taking the complete box out if it ain't proving good.