Targa Rally Car

[Rallyace 3]

I’d like to start a discussion and gain from the experience of others before rebuilding a 1900 8v for Targa Rallying. 

 

For those that don’t know, Targa Rallying is a form of Road Rallying. The events are run in daylight and have off road sections, with a 30MPH average speed, which are timed to the second. Lots of the events are multi-venue, but the road sections are essentially non-competitive, with very relaxed timing. 

 

So onto the engine. I’m certainly not looking to build a highly stressed screamer. In fact the regulations don’t allow it. I’m looking for a strong and reliable engine, with the emphasis on torque. 

 

The pistons and liners on the donor engine look to be almost new, so the bottom end will be virtually standard. New rings and bearings and a careful rebuild will be the extent of the work. I will be running a 26 tooth sprocket on the oil pump, Richard Longman baffles and a 13 row oil cooler. I also intend using a 1600 flywheel. 

 

I have modified a cylinder head following accepted guidelines. I have removed the casting marks on the ports and created a smooth radius on the “short side” radius as the port transitions into the valve guide/throat area. The valves are 3 angle and the guides are phosphor bronze and in good condition. I will have it skimmed to give a compression ratio of 10.5: 1 or 11:1 and have a Piper 270, fast road cam. I realise that this cam receives mixed reviews and probably doesn’t give anything over the standard cam. I have and it’s new so, in it goes. I also have a vernier timing wheel. I have a four branch tubular exhaust manifold and an Ashley exhaust system. I bought the manifold as the standard down pipe is close to the end of its useful life.

 

That’s the background. Now onto the areas that I would like advice with.

I may want to go with a different cam in the future - something like a 280 degree duration. I understand that the standard AFM gets a little unsettled with longer duration cams, so I’m considering a bit of future proofing. Targa rally rules restrict you to a maximum of two chokes if moving away from the standard injection. This rules out Webbers and throttle bodies. Another popular mod these days is to go to four bike carbs. I have actually bought a set of Honda Blackbird carbs. I am wondering whether a pair of these 42mm choke carbs would work well with this setup. I believe that it’s been done on Ford Pinto engines as an alternative to a single 45, or split 40’s. It would, of course, require a bespoke manifold. I don’t currently have any plans for an after market ECU, but I’m open to advice. At the moment, I’m thinking of buying an H&H rebuilt and, advance curve modified distributor.

Am I on the right lines, or are there better ways of getting a really torquey, 130BHP at the wheels engine. 

I don’t want to go 16v and a swap to an engine from another manufacturer is also out. 

I hope that I’ve given enough info on what I’m looking for to keep the discussion focussed.

Thanks in anticipation

 

 

[DamirGTI 323]

Sound like a good plan ...

 

Complete rebuild/recon first then :

 

Good head work , higher compression ratio and performance cam will make for an nice torquey but also rev happy engine (combine with some custom made gear ratios , it can really transform the nature of the car) .. if set up/tuned properly afterwards should be good/reliable .

 

Ignition timing will be one of yours biggest issues you'll need to solve ... the better the solution you find for that the better the end result performance and reliability wise .. OE ignition advance curve is crap for std. engine let alone modified with high CR , for anything over standard dynamic compression ratio in the range 10.5/11.1 you really need reworked/recurved dizzy as an minimum , and mandatory 98/100 RON petrol .. otherwise the engine will detonate itself to death .

 

I would sneak "ignition only" ecu and run it on mapped ignition .. if needed , can be done with leaving the OE dizzy as an signal/trigger (or using VAG dizzy with hall sensor) if the racing inspection is really thorough and strict ... or full SA ECU and hide it , gut out the AFM internals so that it looks original and leave it on .

 

With regards to raising the compression ratio , rather than skimming the head consider 1.9 DFZ pistons with rods if you can find some (handy cos if , for some reason you don't like it , can take the pistons out and reverse the mod back to std. and try something else instead)  , or decking the liners if you have skilled machinist willing to do that for you ... picking either specifically/aiming to decrease the squish height .

 

Expect to see increase in oil and coolant temp. on such modified engine , especially if for racing purposes .. std. cooling system is of a good flow so just colder thermostat and fan thermoswitch , but std. (air-to-air) oil cooler is no good .

 

 

Haven't done much experimenting with aftermarket cams , thus not much to say about that ... Peter will know as well as the rest , he'll be here shortly !

 

 

D

 

 

Edited May 28, 2021 by DamirGTI

[Rallyace 3]

Thanks Damir, 

An ignition only ECU won’t be a problem, as there is no specific reference to ignition, only injection. The ratio’s are as good as I can get with standard 205 GTi gears. I know that there is work that can be done with ratios from other boxes, but my understanding is that the flexibility is with 3rd, 4th and 5th. I’m more interested in 1st, 2nd and 3rd, as what I do is fairly low outright speed. I am running a 4.8:1CWP and a Quaiffe ATB diff. I also have the option of going to 4.4:1 CWP. The oil cooler that I have will, I think, be adequate. It’s a new 13 row Mocal oil cooler. Lots of surface area for the air to do its job and a little bit of extra capacity too. Thanks for the idea about the alternative con rods. I need to take a bit off the head anyway to get rid of a little bit of corrosion/pitting. 

 

Excuse my ignorance, but if I fit an aftermarket ECU, can I run without the  AFM? If so and I can get to my 130 BHP at the wheels, high torque engine, I’ll abort the plan for the bike carbs. I don’t want to go in a direction that isn’t necessary/desirable. Changing the dizzy shouldn’t be an issue. The regulations only make specific reference to the injection. I’m interpreting that as the plenum chamber fuel rail and injectors etc. Would the ignition only ECU run in tandem with the stock ECU for the injection?

Thanks again for your comment. This is exactly the help I was looking for. 

[petert 549]

Why can’t you run a full aftermarket ecu, along with the standard inlet manifold? You won’t need the AFM as you’ll be sensing engine load via a MAP sensor (manifold pressure). 

[petert 549]

I’d also use a box full of Mi16 parts, ie

- pistons, rods and liners

- 22T oil pump sprocket (26T are too soft)

- BE3 Mi16 clutch

- Mi16 or XU10J flywheel, so you have the Motronic 60-2 teeth for the ecu

 

I’d also use a copper head gasket to reduce the squish height and control the CR.

 

If you’re going to run a low cwp, you should consider fitting needle rollers to 1st gear so it doesn’t explode when you grab it quickly on a slow corner. AB Motorsport use to do this mod.

Edited May 28, 2021 by petert

[PhilNW 40]

What are your plans for the rest of the car to match the engine?

 

Gearbox ratios?

LSD?

Suspension?

Brakes?

Wheels and Tyres?

Edited May 29, 2021 by PhilNW

[welshpug 1,621]

if you plan to use a wilder longer duration camshaft you will need to up the compression, seems pointless to go 270 degree now when you really want a 280/300 degree cam.

 

for your use something aimed at rally rather than race, piper used to do a pts gravel rally cam.

[petert 549]

I wouldn't hesitate to use the PTS 7040 cam again, even though it's "top end". Provided you have 11.0-11.5:1 CR, at least 4.43:1 cwp and an aftermarket ECU, it works perfectly on a std inlet manifold. As Welshpug says, I wouldn't be doing the setup twice.

[Rallyace 3]

Thanks PeterT,

 

I like the idea of removing the AFM and I’m sure that, as long as I retain the standard plenum chamber and injectors, I’ll be ok to run an aftermarket ECU. Something from the Magasquirt range?  Does the MAP sensor attach to the plenum chamber? Any further info on a step by step build would be useful. 

I don’t have a Mi16 flywheel and was thinking of buying a Baker BM crank pulley and 36-1 trigger ring. 

I like the idea of the needle roller bearing for the gearbox. I don’t think AB Motorsport is still trading.  Is it a straightforward direct replacement, or does it require  some machining? Do you happen to have the number of the bearing?

I wasn’t aware of the problem with the 26 tooth sprockets. I certainly don’t want to build the engine with a part that is suspect. This could be fortuitous, as I’m currently unable to get hold of the longer chain.

 

PhilNW,

 

I think some of your questions are answered above. 

 

Standard GTi gear ratios. The big problem is the large gap between 1st and 2nd. I’m not aware of a better solution, that doesn’t cost the earth. 

 

I currently have a 4.8:1 CWP fitted, but I have the option to go to 4.4:1. This is something that I’ll assess once the 1900 is in and running. The car runs a Quaiffe ATB LSD.

 

The suspension is Challenge specification Bilsteins. Fixed platform struts. I’m afraid I don’t know the spring rate, but probably something around 180 lbs.

 

The brakes are fairly standard. New standard size discs, with standard pads. The same goes for the drums at the rear. I do run a AP proportioning valve and a hydraulic handbrake, which is modified to be “fly - off”

 

I have some 14” pepper pots with Hankook gravel tyres for when we are allowed to use them. Some events insist on less aggressive patterns. I have machined the centre out of the 14” wheels so that they can be balanced on a standard wheel balancer. I also use 15” GTi wheels with winter tyres for the events that require them. 

 

 

[Rallyace 3]

Thanks PeterT,

 

I like the idea of removing the AFM and I’m sure that, as long as I retain the standard plenum chamber and injectors, I’ll be ok to run an aftermarket ECU. Something from the Magasquirt range?  Does the MAP sensor attach to the plenum chamber? Any further info on a step by step build would be useful. 

I don’t have a Mi16 flywheel and was thinking of buying a Baker BM crank pulley and 36-1 trigger ring. 

I like the idea of the needle roller bearing for the gearbox. I don’t think AB Motorsport is still trading.  Is it a straightforward direct replacement, or does it require  some machining? Do you happen to have the number of the bearing?

I wasn’t aware of the problem with the 26 tooth sprockets. I certainly don’t want to build the engine with a part that is suspect. This could be fortuitous, as I’m currently unable to get hold of the longer chain.

 

PhilNW,

 

I think some of your questions are answered above. 

 

Standard GTi gear ratios. The big problem is the large gap between 1st and 2nd. I’m not aware of a better solution, that doesn’t cost the earth. 

 

I currently have a 4.8:1 CWP fitted, but I have the option to go to 4.4:1. This is something that I’ll assess once the 1900 is in and running. The car runs a Quaiffe ATB LSD.

 

The suspension is Challenge specification Bilsteins. Fixed platform struts. I’m afraid I don’t know the spring rate, but probably something around 180 lbs.

 

The brakes are fairly standard. New standard size discs, with standard pads. The same goes for the drums at the rear. I do run a AP proportioning valve and a hydraulic handbrake, which is modified to be “fly - off”

 

I have some 14” pepper pots with Hankook gravel tyres for when we are allowed to use them. Some events insist on less aggressive patterns. I have machined the centre out of the 14” wheels so that they can be balanced on a standard wheel balancer. I also use 15” GTi wheels with winter tyres for the events that require them. 

 

 

I’m a bit new to this forum and I’m not sure that I’m doing it properly. I seem to be replying to my own comments.

 

Welshpug and PeterT

I think that you are both right when you warn me about doing things twice. 

I’ll try and source a longer duration cam. I don’t want anything too “cammy” as the timed tests are very stop and start and short in overall length. To be fast, I need something that pulls strongly from low revs. They are never high speed. I think that I’ve only been in fourth on a couple of occasions. 

 

 

[welshpug 1,621]

TTV flywheel and an oem crank sensor is a simpler and imo safer method of running a crank signal, especially on a rally car, win win of lighter flywheel and crank trigger in one

[petert 549]

Whilst the TTV flywheel sounds attractive, a standard XU10 flywheel (or Mi16  they're the same part), lightened, is a much wiser and cheaper choice. I've seen the ring gear teeth on TTV flywheels destroyed, and as they're integral and non-placeable, it's expensive if you have an issue. Most aftermarket ECU's accept Motronic 60-2 inputs and Megasquirt would probably be my last choice. I wouldn't do 36-1 when 60-2 is so PSA native. The 1.9L BE3 Mi16 clutch also makes installation and setup so much easier.

 

Mi16 22T sprockets and chains last forever.

 

What's wrong with the gap between a 2.92:1 1st gear and 2nd? Every 1.9L and Mi16 has one.

I have a needle roller in the shed. I'll dig it out.

 

Aftermarket ECU's typically either have an inbuilt MAP sensor or accept an external such as the GM 1 Bar sensor attached.

Edited May 29, 2021 by petert

[Rallyace 3]

Ok. I’ll try and find a Mi16,  XU10 flywheel. I’m assuming that it will be heavier than the 1600 flywheel. How much does it weigh and how much weight can I safely remove?

 

Which after market ECU would you recommend?

 

I’d prefer a longer 1st gear if one was available. There’s approximately 2500 RPM drop when changing from 1st to 2nd. 

As I said earlier, the tests are very slow and tight, which means that the average test will have you up and down between 1st and 2nd a number of times. It would be on my wish list, but not essential. The 1900 with more torque may alleviate the problem.

[PhilNW 40]

On 5/29/2021 at 11:37 AM, Rallyace said:

I currently have a 4.8:1 CWP fitted, but I have the option to go to 4.4:1. This is something that I’ll assess once the 1900 is in and running. The car runs a Quaiffe ATB LSD.

 

The suspension is Challenge specification Bilsteins. Fixed platform struts. I’m afraid I don’t know the spring rate, but probably something around 180 lbs.

 

The brakes are fairly standard. New standard size discs, with standard pads. The same goes for the drums at the rear. I do run a AP proportioning valve and a hydraulic handbrake, which is modified to be “fly - off”

Traction is everything on Targas, better with a plated diff than an ATB

 

Check suspension geometry especially camber, might be worth thinking about some sort of adjustable setup. My 205 came with negative camber on one side and positive on the other as standard, not ideal

 

Uprated pads probably needed, standard drums OK.

 

 

[Rallyace 3]

Thanks Phil. I agree with you when you say that traction is everything. The ATB came with the car, so running it at the moment. I may get a plated diff in the future. I’ve done a handful of events so far. Managed a 2nd O/A in the historics on the Pennine Targa and 8th O/A on the Oaks Trophy, that event didn’t have a section for historics. I’ve actually ruled myself out of the historic class at the moment, as I’ve fitted a Corsa EPS.

I’ve set my home workshop up now, so I’ll probably modify some bottom arms, or possibly turn some adjustable top mounts, so that I can play with the geometry.

The brakes don’t get hot enough to need competition pads. Short blasts, followed by road sections. And they don’t need to be warmed up before the first test.