Mi16 Engine On Webers Rolling Road

[driversdomainuk 8]

Hi

 

My 205 Mi16 has just had a rolling road session at Shropshire Automotive.

 

Spec:

 

forged rods and pistons/knife edge crank

weber 45 carbs

fast road cams

 

The car got 173bhp...they managed to increase it from 162bhp. I know you should not read too much into the figures but I was expecting more...like 190bhp+

 

They got most power from the cam/exhaust timing. They suggest that the cams I have are not great and even the standard cams can make more power....

 

I think it is time to get rid of these fast road cams and go for some rally cams...

 

Does 173bhp sound ok with my setup - would 190bhp be realistic with rally cams increased CR..?

[Sandy 189]

Mapped ignition is the key to good results on carbs IMO.

[tri_longer 25]

Mapped ignition is the key to good results on carbs IMO.

 

Could you expand on your reasoning behind this as I am intrigued whether it would be worth going to mapped ignition on our 8v.

 

Cheers Chris.

[driversdomainuk 8]

anyway back to my question..

 

Is 173bhp a decent figure? - I am not that impressed but again, its chasing figures which to some extent are meaningless.

 

I know some guys who complete never get rolling road figures for this very fact.

[phat205 0]

My Mi16 runs 225 BPH with a 78BHP shot of N20, it's become slugish over the last couple of months so i think its due a tune up.

 

I would be interset to see if it reaches the figure again.

[James_R 3]

fast road cams is a little vague, with ITB's and the bottom end you have why not have the biggest cams you can get away with?

[Sandy 189]

anyway back to my question..

Was I off topic?

 

With the benefit of having mapped a few engines on carbs, I know that a distributor can come close to the optimum ignition on most standard engines, but add multiple throttles and more so lairier cams and the ideal ignition curve is a long way off what can be achieved mechanically.

 

The lowest advance figures will be around idle and peak torque *usually*, peak power and part throttle require higher figures most of the time, but lower rpm and especially lower rpm 1/2 to 3/4 throttle, you'll get a danger zone where catastrophic damage can occur with too much advance, at the same speeds however, full throttle might well need a higher figure. The compromise you have to accept with a distributor is either to run less advance than ideal at most speeds/loads or run the risk of detonation and lose power there instead.

[driversdomainuk 8]

Was I off topic?

 

With the benefit of having mapped a few engines on carbs, I know that a distributor can come close to the optimum ignition on most standard engines, but add multiple throttles and more so lairier cams and the ideal ignition curve is a long way off what can be achieved mechanically.

 

The lowest advance figures will be around idle and peak torque *usually*, peak power and part throttle require higher figures most of the time, but lower rpm and especially lower rpm 1/2 to 3/4 throttle, you'll get a danger zone where catastrophic damage can occur with too much advance, at the same speeds however, full throttle might well need a higher figure. The compromise you have to accept with a distributor is either to run less advance than ideal at most speeds/loads or run the risk of detonation and lose power there instead.

 

 

What mapable ignition would you suggest?

 

How much would the typical cost be, what would be included and what sort of time would it take to fit?

 

Cheers

[Guest Skeleton]

Is 173bhp a decent figure? - I am not that impressed but again, its chasing figures which to some extent are meaningless.

 

I don't think its that great.... You also have to take into account the quality of the dyno opperation, and if they guessed the right drive loss percentage to add back onto your bhp figures. (but im sure they were a trust worthy oppertor)

 

Also, I'd really like to know what kind of compression ratio are you running with those forged pistons?

 

As for tuners not wanting to messure their power output, I don't think gaining any knowledge is a bad thing. Gaining knowledge leads to gaining understanding. You've put money into your car and you wanna see if it was worth it, makes alot of sence to me. I find this usually coinsides with the use of carbs on injected engines, for those who are too lazy to take the time to understand the mapping of high performance fuel injection. (just my opinion, i'm made of wool so don't flame me)

Edited September 8, 2007 by Skeleton

[oliver17491 0]

i would go for a mappable ignition as there quite cheap and they allow you to chage the timing at different rpm's. They say that the biggest hp gain for the money are the cams get some 165's or somthing so it is still drivable on the road but still gives more when you 'come on the cam'.

[Sandy 189]

What mapable ignition would you suggest?

 

How much would the typical cost be, what would be included and what sort of time would it take to fit?

 

Cheers

The rough costs are about £250-400 for the ECU depending on make/type, plus coilpack ~£30 and loom.

Mapping will usually only require a short session in the rollers and some road driving to test, around £200 typically.

Alot more expensive than a distributor obviously, but much nicer end result.

[oliver17491 0]

dont think so, megajolt is about £120-150

[Mattsav 1]

It does sound dissapointing for the spec.

 

What is the CR?

What are the cams?

[taffycrook 2]

Guy's try and be helpfull when posting

 

I don't know the rollers you used so I am not able to comment on the figure, but it does show the value of using the dyno.

For your current set up that could well be the best you are going to get. Or it may not be.

You may gain some power by using mapped ign, but the peak figures don't tell the full story.

Whats the curve look like?

How much torque is it producing and through what rev range?

Mapped ign may help all of this and make it much more pleasant to drive.

 

Typical figures for mi16's in 205's on the rollers I use are;

std 160-165

Inlet cam on injection 175

Std on 45's 175-180

cams on 45's 185 (repros inlet only fast road)

tb's rally/race cams 190-210

autograss engine 240-250

 

Transmission Losses tyical 30-35 bhp depends on gearing.

So minus 30-35 for @ wheels figures.

 

Things to check if you are missing power.

Choke size

exhaust

Cylinder leak test

full throttle

 

Do the above before spending any money on performance parts.

[driversdomainuk 8]

Guy's try and be helpfull when posting

 

I don't know the rollers you used so I am not able to comment on the figure, but it does show the value of using the dyno.

For your current set up that could well be the best you are going to get. Or it may not be.

You may gain some power by using mapped ign, but the peak figures don't tell the full story.

Whats the curve look like?

How much torque is it producing and through what rev range?

Mapped ign may help all of this and make it much more pleasant to drive.

 

Typical figures for mi16's in 205's on the rollers I use are;

std 160-165

Inlet cam on injection 175

Std on 45's 175-180

cams on 45's 185 (repros inlet only fast road)

tb's rally/race cams 190-210

autograss engine 240-250

 

Transmission Losses tyical 30-35 bhp depends on gearing.

So minus 30-35 for @ wheels figures.

 

Things to check if you are missing power.

Choke size

exhaust

Cylinder leak test

full throttle

 

Do the above before spending any money on performance parts.

 

 

I am using the Group N OMP exhast from the 8v engine. I am also using the modified exhaust manifold from a compnay found on eBay. All fitted together ok.

 

Before I go chasing figures I will see what times I get at next hill climb end Sept.

[boldy205 74]

I presume you are using a 205GTI dizzy? If so then you have got to remember, and im supprised no one else has said about, is the fact that its not the correct dizzy for the engine , unless it is weighted accordingly. When i had my standard MI on Weber 45s (using the 1.9GTI dizzy) The car made poor power, only just 100BHP at the road wheels. The Rolling road operater set up the carb jets and choke sizes to what he had experiance with before and then set about the ignition timing. Eventually he ran out of ignition advance and the engine was still making power, in the end on FULL advance the road wheel figure was 131.5 (aprox 165-170 BHP at fly)

This shows that with more advance (at full throttle) there is a good chance of making more power.

Because its running full advance (with no vac advance due to pulsing) the car is not very nice on light throttle but stick you foot down and its great!!

So what im getting at, is fitting mappable ignition will allow you to remove the whole ignition setup and replace it with a ECU, which gathers info from the engine via crank speed, throttle position or vaccuum, and advances/retards the ignition to suit. and its supposed to be very accurite.

I am in the process of collecting parts for a Megajolt setup, which uses their own ECU and Ford EDIS components.

PM me if you would like to know more as i can put you in touch with a VERY helpfull man who knows about/sells them.

[driversdomainuk 8]

I presume you are using a 205GTI dizzy? If so then you have got to remember, and im supprised no one else has said about, is the fact that its not the correct dizzy for the engine , unless it is weighted accordingly. When i had my standard MI on Weber 45s (using the 1.9GTI dizzy) The car made poor power, only just 100BHP at the road wheels. The Rolling road operater set up the carb jets and choke sizes to what he had experiance with before and then set about the ignition timing. Eventually he ran out of ignition advance and the engine was still making power, in the end on FULL advance the road wheel figure was 131.5 (aprox 165-170 BHP at fly)

This shows that with more advance (at full throttle) there is a good chance of making more power.

Because its running full advance (with no vac advance due to pulsing) the car is not very nice on light throttle but stick you foot down and its great!!

So what im getting at, is fitting mappable ignition will allow you to remove the whole ignition setup and replace it with a ECU, which gathers info from the engine via crank speed, throttle position or vaccuum, and advances/retards the ignition to suit. and its supposed to be very accurite.

I am in the process of collecting parts for a Megajolt setup, which uses their own ECU and Ford EDIS components.

PM me if you would like to know more as i can put you in touch with a VERY helpfull man who knows about/sells them.

 

Thanks for that - interesting. But I think I will stick with the 8v dizzy for the time and might move over to mapped ignition sometime. Think I will be reducing my times by fitting 350 lb springs with coilovers as the front is still too soft.....its all money in this game!

[driversdomainuk 8]

It does sound dissapointing for the spec.

 

What is the CR?

What are the cams?

 

 

Hi

 

I have emailed QEP recently to spec me out a set of cams for this setup - currently waiting. At moment it is running kent fast road cams and the CR is standard as far as I know.

[TT205 42]

............... and the CR is standard as far as I know.

 

 

I think most people reading this thread will have presumed you HAVE upped the compression and made their comments on this basis (I could be wrong though)

[driversdomainuk 8]

Hi

 

 

News Update:

 

The figures I got as stated = 167bhp.

 

However, it only occured to me recently! I have a shift light which was setup for my 8v and came on at 5900rpm. I had not changed this with the new engine, and ave NEVER run a rev limiter

 

I think (will comfirm) that the garage took it to 5900rpm, saw the light flash and then eased off...figuring it should not rev anymore...

 

167bhp at 5900 rpm when max revs is at 8000rpm means, and I hope the true figure is more like 185+bhp....

 

Realistic thought...?

Edited October 1, 2007 by driversdomainuk

[VisaGTi16v 1]

No idea on the figures but why was your old shift light set so low? Peak bhp on a standard 8v is over 6k I thought so yours which was presumably not std must have been higher? I set my shift light for about 150rpm below the limiter.

[driversdomainuk 8]

No idea on the figures but why was your old shift light set so low? Peak bhp on a standard 8v is over 6k I thought so yours which was presumably not std must have been higher? I set my shift light for about 150rpm below the limiter.

 

It was set at 5900 as the max power was around 6200. I worked on the basis that by the time I had seen the light the time delay in getting my hand down to change gear, the revs would be around the 6200rpm

[VisaGTi16v 1]

Fair enough may want to look at your RR graph to be sure though, certainly get one for this new engine now that you know it can rev higher. My peak bhp is at 6600 but it stays flat till 7200 (possibly due to maxed out injectors or cam profile) so its still better than I hold on and change just under 7200 as it means higher rpm and thus bhp when in the next gear up, if I changed at 6600 it would drop down too low

[driversdomainuk 8]

Fair enough may want to look at your RR graph to be sure though, certainly get one for this new engine now that you know it can rev higher. My peak bhp is at 6600 but it stays flat till 7200 (possibly due to maxed out injectors or cam profile) so its still better than I hold on and change just under 7200 as it means higher rpm and thus bhp when in the next gear up, if I changed at 6600 it would drop down too low

 

 

But surely the graph would level off at "max" rpm as the would have realised it was on the red line and held off, regardless of it being flat or still increasing in power..?

 

I think the graph did NOT appear to go flat, just sort of stop mid flight which I know some do anyhow if an engine pulls right up to its red line..correct??

[VisaGTi16v 1]

Do you actually have the printout as from your post on the previous page you implied you didnt as you were going to ask them what revs they took it to? Surely they gave you a printout, if it doesnt have revs but just road speed you can (very tediously!!) work it all out going backwards as long as you know your gear ratios, work out tyre diameter etc which is what I had to do with mine. I am no expert but most printouts ive seen certainly of the mk2 Mi16's in zx's and S16's are still rising as they hit the limiter. Mine tailed off at 6600 which was at 168bhp but with original injectors which only flow to 180bhp and my cam profile is something like "2500-6500" so I presume its related to one of them

 

Here is mine so you can see I dont upshift until just before 7200 though as its still better to hold the gear as power isnt dropping off and means higher rpm/bhp when I go into the next gear