8v Vs 16v Power/torque Comparison

[Anthony 1,000]

From reading various threads on here about owners of 8v GTi's looking to upgrade to Mi16 power, there's always one question that comes up time and time again - that of low down torque.

 

When I was thinking of getting an Mi16 engine, this is something that I was worried about as well - I really liked the torque of my 1.9 8v engine, and other old-school 16v engines that I'd driven were completely gutless below about 3500-4000rpm.

 

For those of you with the same concerns, let me put your mind at ease now that I've got both an 1.9 8v and a 1.9 16v - you really don't have to worry, as the Mi16 is probably the best 16v NA engine I've driven for low down torque (certainly the best engine without VVT that most modern engines have)

 

Both the cars are running on 1.9 gearboxes and both weigh about the same, so it's a pretty fair test. There really is little difference between the 8v and 16v engine's below about 4000rpm - the 16v lump is quite happy lugging along below 2000rpm. However, go past 4000rpm and the engine note becomes more angry and just keeps pulling and pulling, only starting to let off as you hit 7000rpm - long past where the 8v is getting breathless.

 

Basically, if you think of it as a 8v engine that has some incredable headwork and decent engine management, I don't think you'll go far wrong. It is nothing like most 16v engine's I've driven - it really is close to an 1.9 8v when it comes to low end. Of course, I suspect that a tuned 1.9 8v with headwork is likely to have more torque low down, but certainly comparing standard engines, the Mi16 is close if not equal.

 

The only noticeable difference I've noticed is with throttle response - the 8v lunges forward instantly when you press the loud pedal, whereas the 16v seems to be a little more progressive and doesn't lunge in the same way - I assume this is partly due to the engine management, and partly due to the single vs dual throttle butterflies. The throttle response certainly isn't bad though, and is still far better than many engines (the throttle response on my friends Focus 1.8 Zetec was awful in comparison)

 

So there you have it, low down torque and top-end power - you can have your cake and eat it

Edited January 10, 2004 by Anthony

[fiji bob 0]

wonder what it would be like with a 1.6 final drive :hint: :hint:

[Steve.C 0]

slip a 1.6 g/box on the Mi16 and then come back with your findings

[petert 550]

The only noticeable difference I've noticed is with throttle response - the 8v lunges forward instantly when you press the loud pedal, whereas the 16v seems to be a little more progressive and doesn't lunge in the same way - I assume this is partly due to the engine management, and partly due to the single vs dual throttle butterflies.  The throttle response certainly isn't bad though, and is still far better than many engines (the throttle response on my friends Focus 1.8 Zetec was awful in comparison)

It's all about gas speed. The Mi16 has larger ports and valve area, thus lower gas speed at lower RPM.

 

Your right though, a std. Mi16 has more torque every where, when compared to an 8V.

[cybernck 400 1 Cars]

i completely agree with anthony, both on low-down torque and throttle response.

 

 

mi16 DOES NOT have less torque than 8v ANYWHERE in the rev-range.

 

and there were graphs posted to prove it a while ago.

 

 

by performing an mi16 conversion, you gain the power from 4000-4500 rpm on,

and extra 500-600 revs to play with .

[sleeper205 0]

can anyone dig out those graphs?

 

might be intersting to do a 8v vs 16v race where both cars have the same gearbox and change gear at the same point.

 

would be close wouldn't it?

[NickR 10]

Yup I gotta agree, but when you compare a tuned 8v to a std mi16 (2 comparable conversions cost wise), you find the 8v is better for mid range, but then the mi16 is damn good at high revs, makes it hard to beat.

[atomic-jon 1]

thats the main reason why im happy with a tuned 8v, the low rev performance, its a bit more convenient for daily driving, but sure the 16v is great when you want up to the limiter action

[Dream Weaver 2]

But you cant beat the "fire breathing dragon" roar when the Mi takes off at 4k rpm

[cybernck 400 1 Cars]

might be intersting to do a 8v vs 16v race where both cars have the same gearbox and change gear at the same point.

 

would be close wouldn't it?

well i've done the said race but with cars going to their max power (6000 rpm for the 1.9 and 6500 for the mi16).

 

i'll post more about it later.

[mos 1]

Hi,

 

i dug this topic out using the search function as i have some cash burning a hole in my pocket and i want to take my 1.9s on 45 dellortos to the next level.

i am suprised to read the 8v verses 16v torque situation

i have for the past 11-12 years of 205 gti ownership been convinced by what i have been told/read that the 16v is flat and breathless below 4k and the 8v was the engine to stick with if you wanted torque etc.

well it appear i got that very wrong!

i was going to post a topic asking what was the best route for a 8valve solely road car that must spend 70% of the time below 4k and the rest above, i.e big valves different cams etc be suitable or are they really only of benefit on a track car.

 

having read this i am thinking i should perhaps be considering the Mi 16 route.

any advice anyone.

 

if i do go down the 16v route what would be the best option in terms of engine choice, i think from what i have read here that the 2ltr iron block is the better option as its has a bit more torque

obviously i would like to retain the carbs, would i need a new inlet manifold and what would be the best modifications to do the head (can i go a bit hotter cam wise because i am running carbs not injection) or mods to the whole engine for that matter for a road going car, i would like to retain the low down grunt where possible.

 

what sort of power output could i expect with a modded 16v running cams and a longmans modded 8v dizzy that gives 20 degrees advance btdc at idle and 32 degrees all in at 4500rpm (would i be better running a standard dizzy) or for that matter would a mapped ignition system deliver worth while benefits on a road car.

for that matter would there be many gains to be made by replacing the carbs with throttle bodies.

 

i never even considered a 16v before because of the torque issue so this is a whole new kettle of fish to me and as such i am reconsidering everthing to do with my engine set up

 

please help!

 

thanks

[S33GAV 0]

well i've done the said race but with cars going to their max power (6000 rpm for the 1.9 and 6500 for the mi16).

 

i'll post more about it later.

Did you post results/info about this test in another thread?!

 

Edit: just noticed this is 2.5 years old!

Edited July 27, 2006 by S33GAV

[Dino 3]

- I wondered where this thread came from and then noticed how old it is!!

 

All of this 8v vs 16v torque issue is quite subjective. Certainly my 16v has more torque than an 8v but doesnt *feel* like it has as much as an 8v. Then again I've always found 8v 1.9s feel breathless after about 4.5k (due to where the torque curve tops out) whereas my 16v's torque curve tops out at 6650rpm IIRC which makes for a very frantic top end experience!

 

I used to be an 8v afficionado but since having my 16v lump installed 19 months ago I've never looked back.

[TEKNOPUG 3]

Hi,

 

i dug this topic out using the search function as i have some cash burning a hole in my pocket and i want to take my 1.9s on 45 dellortos to the next level.

i am suprised to read the 8v verses 16v torque situation

i have for the past 11-12 years of 205 gti ownership been convinced by what i have been told/read that the 16v is flat and breathless below 4k and the 8v was the engine to stick with if you wanted torque etc.

well it appear i got that very wrong!

 

You need to turbocharge it if you want a lot of torque: think 180lbs/ft + from 2k onwards.

[dazEmad 0]

Hi,

 

i think from what i have read here that the 2ltr iron block is the better option as its has a bit more torque

 

I agree my m8 has the alloy block also running on 1.6 gearbox and he also says my iron block has more power upto 4000 rpm. The alloy block seems more punchy when it hits 4000 rpm where as the iron block is more smoother. We have had a few drag races when my new engine had only covered 500 miles with me carrying a passenger, he had no back seats and there wasnt really much in it. Now the engine is over 1000 miles it feels much looser now and better on the pick up so we will see what happens on the re-match tonight on the way to the South Yorks Meet.

[petert 550]

what sort of power output could i expect with a modded 16v running cams and a longmans modded 8v dizzy that gives 20 degrees advance btdc at idle and 32 degrees all in at 4500rpm (would i be better running a standard dizzy) or for that matter would a mapped ignition system deliver worth while benefits on a road car.

for that matter would there be many gains to be made by replacing the carbs with throttle bodies.

 

that's probably the worst thing you could do. The Mi16 needs mapped ignition to get the best low-mid range torque. The finished curve is anything but linear.

[kyepan 291]

The only noticeable difference I've noticed is with throttle response - the 8v lunges forward instantly when you press the loud pedal, whereas the 16v seems to be a little more progressive and doesn't lunge in the same way - I assume this is partly due to the engine management,

I have two mi16's at the moment, one running 8v management and one propper 16v one, the 8v management lunges at the slightest tickle of the loud pedal, the 16v is progressive in its uptake.. like anthony said.

Edited July 27, 2006 by kyepan

[mos 1]

I have two mi16's at the moment, one running 8v management and one propper 16v one, the 8v management lunges at the slightest tickle of the loud pedal, the 16v is progressive in its uptake.. like anthony said.

 

are these running carbs, does that make a difference i.e no lunges when carbs are used to replace injection.

[Daz_C 8 1 Cars]

IMO unless you are definatly going to mod the 16v I'd stick with your SBC 1.9S. I don't think you would be happy with it otherwise !

When I was at Bruntingthorp for the FCS I had a good run with a GTI 6'd 205 and there was very little in the performance. Where I gained in certain places he pulled back in others and visa versa. I was running my SBC 8v on injection. Your running Carbs !

I'd see if you can get a drive of a 16v 205 in standard form and one of a spec that you might be thinking of before you take the plunge.

[Garry 1]

Wonder who that was ^^^^^^^

 

I was surprised actually how quick Daz C's car was, I was a bit miffed when I saw it was 'Only' an 8v.

Edited July 27, 2006 by Garry

[PumaRacing 1]

I've never understood this myth that 16v engines don't have good torque. Clearly they have more peak torque per litre than 8v engines. The general tuning article and the power and torque articles on my website look at torque per litre targets for both types of engine. 16v engines have about a 10% advantage in peak torque per litre in both standard and modified forms.

 

At very low rpm maybe the 16v engine shows a bigger drop from its peak value than the similar 8v engine but without actually dropping below the 8v numbers. This makes it feel a little gutless compared to when it's on song but it's only a relative thing. My own Focus 16v grunts away quite happily at 1000/1500 rpm though and has a very linear torque curve apart from the flat spot at 3500 rpm.

 

What really is hard is getting 8v engines up to the sort of peak torque that 16v ones show very easily. As standard the 8v engines I list on my website have an average of 63 ft lbs per litre. The 16v ones have an average of 70 ft lbs per litre.

 

You need to do some pretty serious tuning just to get an 8v engine up to that 70 ft lbs. The 1360 TU that I've been working on for my friend Garry in Aberdeen is now showing nearly 140 bhp (just over the magic 100 bhp per litre) now and peak torque at 99 ft lbs is 72.7 ft lbs per litre. It's had dozens of hours of dyno time invested in it trying different ram pipe lengths on the TB's, cam timing etc and I don't think there's much more to come. Beating 73 ft lbs per litre is tough. I show higher targets on my website but I don't say how hard they are to achieve. Maybe from big bore/short stroke engines where you have lots of valve area but not from the small bore/long stroke Pug engines which are air starved regardless of state of tune. The worst is probably the 1.9 8v XU which has a horrible bore/stroke ratio and tiny valves for its capacity. It's actually more like a diesel engine than a petrol one.

 

By comparison I posted some Zetec power figures on here a couple of months ago. One engine with DCOE's and the other with TB's and cams. One made 76.5 ft lbs per litre, the other made 77. Very easy to achieve. Just slap on a decent exhaust manifold and system, a decent inlet manifold and TB's and maybe cams and you have your 10% gain over standard in torque per litre terms. Of course the same could be done with an 8v engine which would bring you up from 63 to 70 ft lbs per litre.

 

However, try getting yet another 10% to achieve 77 ft lbs per litre from an 8v engine. Basically you can't, or at least not without extreme difficulty. Even if you could achieve it at peak torque, try doing it and also retaining good torque down at lower rpms. High peak torque tends to come from long duration cams which generate very strong induction system pulses. However they also stop working at low rpms. With the TU we've achieved a power band from 3k to 8k. Basically by lots of head work and not too much cam. I think we could pull a little more peak torque with a hotter cam but we'd lose the pull out of slow speed corners. That tractability is what makes the car so fast on rally stages.

 

If you have an 8v engine with more than 73 ft lbs per litre you've got a gem. If you have one with that and also a long power band you've got a very rare beast indeed.

[Jonmurgie 2]

So Dave, Sean's 8v seems to be giving 76 ft lbs per litre is as you expected then? I think people are waiting with baited breath for you to pass your comments/thoughts on his results etc.

[Sandy 189]

I think the usually sharper throttle response of 8v engines is often mistaken for torque. Most likely due to lower parasitic losses and smaller port/valve curtain area.

[mos 1]

Hi,

 

i have just been over to the puma racing website and here is my thinking based on the very insightful info on there.

 

 

at this point i should point out that i originally aquired the 1.9s engine cheaply second hand rather than having it built myself, obviously i confirmed with skip brown it was genuine first. just as i was about to order a head from skip brown this engine popped up in the local loot and seemed a bargain

running a skip brown 1.9s with dellortos a set up like this would be lucky to be clearing say circa 150bhp,

this is further compounded by the fact that i have discovered when i reconditioned my head last year that the head is originally an early 1.6 uxj5a and as such runs smaller valves, i assumed these would have been substituted for the larger later valves when skip brown converted the car back in 89/90.

once the head was off and i compared them to later valves it became apparent this is simply not true.

spoke to skip brown and they confirmed this saying it was impossible to fit the larger later valves into an early head (wish they told me that before i bought it and i would have walked away)

point is i have effectively got a small valved gas flowed head with cam running carbs i would have though i would be lucky to actually be producing 140bhp

i had intended to use the money i have to replace this head with a big valve head and slightly hotter cam

now based on daves website even if i was to replace this head with one of his big valve heads with a hotter cam, but not too hot as it is a road car, i would be lucky to see 155-160bhp

about the same as standard mi16,

now i would not fit the unit as standard

i would either source the engine myself or let the engine builder i decide to use source one and then get them to replace anything on the bottom end that needs replacing and build me a big valve head with cams suitable for road use with carbs but not too hot as i would like to retain as much low end torque as i can

based on daves website this should net me somewhere in the region of 200bhp whilst giving a decent low end pull

yes its going to csot me a lot more but at least i will be able to sell my 1.9s on ebay etc to offset some of that extra cost but i believe the extra power/torque will be worth the cost

 

please guys if i am wrong do tell me i am certainly no expert on this stuff

 

thanks

 

mark

[smckeown 1]

it's been proven you can get ~190 from an mi16 with a standard head, standard cams on TBs. Search for Mattsav's posts