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My cars - Second chapter

I am sitting in a long hauler bus and it is 7 am. I  woke up an our earlier and in three and half hours I will see,  lets hope so, my  next car. If it appears to be as advertised, it will be another four hours drive back. A perfect way to spend a saturday.

The red MX-5, which this blog originally was about, was sold one year ago. I had it for over ten years and it basically was nothing but a pleasure. Sure, we had some downhills too, but really there was nothing wrong with that car. And boy oh boy, that 8500 rpm redlining 173 bhp naturally aspirating four banger was pure ear candy. Despite all of that somehow my thoughts began to shift towards older vehicles, perhaps ones with a hint of historical value and 70's flowing body lines.

So why has it taken a year to get to this point? I went to see and test drive a couple of candidates during the summer while last winter was spent with other activities. Two BMW 1502s fell into 70's category. BMW's driver oriented reputation compensated the lack of flow in the body styling. The better example was in very good condition but unfortunately the lack of use was clearly felt in the ride quality. A couple of Datsun 180B's were on offer too. The better one was in original condition, reasonably priced and to no one's surprise was sold in couple hours. The other one, which was in SSS trim, revealed to be in poor condition. Most of the bits and pieces were there but the corrosion was wide spread and the paint was - well, a money pit with a capital p.

I even explored the early 80's super car option. Early Porsche 928s were very tempting in many ways. The better samples are expensive for a reason and vice versa. I drove one 928S with automatic transmission. It had over 200 thousand klicks on the odo and six or more owners. How should I put it? In the kind of condition a Porsche 928 deserves to be, that car would have been a wonderful piece of German engineering. But that one was not. And I was not going to be the one who spends a fortune to bring it to the original glory.

So here I am sitting in a bus with three more hours to go. Will that 42 years old, low mileage, four seater, two door sedan win my heart? Most likely yes, but nothing is sure until it is sure.

Klaus Ludwig’s 1988 DTM Title Winning Ford Sierra RS500 Cosworth - Alive Again!

The one and only, the legendary, Klaus Ludwig’s 1988 DTM title winning car Ford Sierra Cosworth RS500 is presented in its original winning glory. Where? In Finland – of course! This unique piece of European racing heritage is so amazing that it deserves to be brought into public attention.

The owner of the race car power house - Sarlin Race Team - Kalle Sarlin did not just win the Finnish Touring car championship with this same Sierra Cosworth in 1991, but he also took the time and effort to take this classic back to its original glory.

Kalle and his crew started the restoration of this fine piece of machinery about ten years ago. It has taken hundreds of hours to get it to this point where everyone can let their eyes feast on its beauty. The restoration began from the bare body shell and continued step by step until the current state was reached.

Nowadays to an untrained eye it might just look like another Ford Sierra with some stickers on it. But to all of you guys who know what to look for its obvious that this beast is nothing but business. Wide racing slicks wrapped around three piece BBS magnesium alloys with center-locks are yelling “No, it is not another tuned 3-door Sierra with graphics”.

Under the bonnet lurks a turbocharged 2-litre RS500 racing engine. This Ford’s YB-series 16 valve DOCH inline four has been seriously refined to be able to take the heat of the continuous racing. Garret’s T3/T4 turbocharger feeds compressed air to the engine through a big air-to-air intercooler. Group A cylinder head and Group A pistons guarantee that neither the airflow nor mechanical strength becomes an issue. Three external fuel pumps and 8 injectors make sure that the air fuel ratio stays where the Bosch Motronic MP1.7 engine management system commands it to be. Roughly 480 hp is transmitted to the rear wheels through a sand casted Getrag 5-speed gearbox and a Ford Motorsport 7.5” differential. Both gearbox and differential are cooled with PWR oil coolers.

What is a race car without a proper suspension and brakes? A street car, perhaps. Well, in this case nothing but Ford Motorsport Group A magnesium uprights, Group A magnesium rear arms, quick steering rack, Bilstein coil-over shocks (front/rear) and adjustable front anti-roll bar are there. The brakes are from AP-racing with 4-pot calipers front/rear and vented rotors 330x35 mm front plus 304x28 mm rear.

As if all of the above mentioned was not enough, the list of the goodies goes on: Factory RS500 front lip spoiler, bumpers, twin rear spoilers, heated windscreen, seam-welded chassis, FIA-spec multipoint roll cage, air jacks, Recaro SPA carbon/kevlar seat, 6-point harness, Bosch Motorsport LCD display and so on...

Oh, what mechanical beauty.

Article update: Cossie has found a new owner, and I have been told, had some serious track time on the Nürburgring!

Follow SRT also in facebook:

https://www.facebook.com/sarlinraceteam

More NA POWER part 5: 100 bhp per liter in 1.7 liter B6ZE

My engine tuning project has finally achieved its goal - to make 100 crank hp per liter in naturally aspirating form. Current maximum figures are 173 hp of power and 181 Nm of torque (crank). And max figures are not all, torque peaks up at 4000 rpm and there is usable power up to 8000 rpm. Let’s first take a brief look at the previous modifications and then inspect the current setup a bit closer.

In 2008 basic bolt ons with oem cams produced 132 crank hp and 151 Nm (105 rwHp and 124 rwNm). That was all I could get out of a 1.6 liter engine with bone stock internals and a larger RX-7 AFM.

In 2009 the engine was bored to 1720 cc with high compression (11:1) Toda Racing pistons. The head was mildly ported with oem valves which were left untouched. Also Toda Racing 272/9 cams (in&ex) and solid lifters with stiffer springs, measured to be good for 8300 rpm with safety margin, were installed. Conrods were still the old ones with about 140 000 km behind. There were no adjustable cam gears and the catalytic converter was bone stock, also possibly clogged. Van Kronenburg Management System’s fully adjustable ECU was wired to have a command on the injection and ignition. This setup produced 156 hp / 175 Nm (121 rwHp / 147 rwNm). After the build I had almost two years of happy high revving when the original conrods finally gave up. It luckily happened with no drama as the engine suffered a spun rod bearing.

Forged Toda Racing pistons (3 mm oversize) and CP Carrillo A-beam rods, 110 grams less than stock.

In 2011 as the engine was torn apart for the bottom end rebuild the cylinder head also went under maintenance. The block received a factory new long nose crank, Carrillo A-beam rods, ACL Race Line bearings, Toda Racing pistons and Toda Racing light weight flywheel - all dynamically balanced.  New valve guides were installed and stock valves received a three angle grind to improve the head flow. Old cam gears and worn cat were replaced with Toda Racing adjustable gears and Catco’s metallic 400 cell unit. Instead of the standard 1.0 mm thick head gasket a 0.8 mm thick optional part from Toda Racing was installed to increase the compression ratio to about 12:1. I also wanted to lower a bit high intake air temperature and fabricated a sealed airbox that was supposed to produce a ramming effect in higher speeds. With revised cam timing this setup produced an estimated 160 crank hp. Crank power is estimated because this time a hub dyno was used and the measured figures were 132 rwHp and 142 rwNm. I was getting closer to my 100 crank hp per liter goal!

During the 2011 dyno session it was noticed that the original throttle body started to restrict the flow (a vacuum was building in the intake manifold over tb). Another visit to the hub dyno was made in 2012 with a new 60 mm diameter throttle body installed and ported to the intake manifold. The result was a bit disappointing with only minimal gains (135 rwHp and 145 rwNm). At this point the airbox started to be the main suspect for creating a bottleneck.

AT Power 60 mm 'Shaftless' throttle body required some porting to the intake manifold.

Finally this spring I made the latest to the dyno (inertia type once again). A wanted to make a back to back comparison with the old airbox and the new “cold side” cone filter intake. I prepared for the dyno session by checking the valve lash and noticed that they all were on the loose side. Meticulous adjustment to the specs (0.20 mm intake and 0.25 mm exhaust) was done. I also checked that the intake manifold was port matched to the head. First pulls on the dyno with the old airbox indicated restricted flow above 5500 rpm. Peak torque was 159 rwNm at 5000 rpm and after that the curve sank to about 150 rwNm. Max power was 138 rwHp.

After that the new intake was installed and it was time for the final pulls. And there it was! The torque stayed up till 6750 rpm, and maximum output of 173 crank hp (144 rwHp) was achieved.

What is the most noteworthy, in my opinion, is that this motor runs on a stock intake manifold, although port matched. The head porting is also mild, I would call it a “fast street porting”, and stock sized valves are used. The potential of producing current figures has always been there but the output has been hampered with various restrictions. In the very beginning it was the displacement and cams. Then it was the flow of the cat, improper cam timing, restrictive throttle body and intake plumbing.

So, what is the current bottleneck? Evidently there is something restricting the flow above 7000 rpm. Intake runners, stock valves, current cam profiles, exhaust manifold, 2” catback exhaust pipe or something else. Stretching the power band 800 – 1000 rpm higher would be good for another 15 to 20 hp. We will see…

Miata Camber Gain and Latest Suspension Mods

It was about time to get rid of the original rubber bushes that had taken the beat at the track and resisted the wear and tear of road use for 23 years. I installed a complete set of Energy Suspension poly urethane bushes during the winter. The job was quite straight forward and I could complete it in my ordinary garage. It took some time but I was not in a hurry.

I also wanted to replace my old Koni Sports Kit with something more suitable for racing. Most of the track oriented guys here in Finland have opted for BC Racing. They seem to work nice and customers are satisfied. I must admit having an issue with BC-racing shock coming from Taiwan. I also don’t like the high spring rates they use. I know, they are not all bad and BC’s kits evidently work nice. Another issue was money. Bilstein, Öhlins, KW, AST, JRZ and Koni all make excellent shocks and complete kits, but they come at a price – too high for me.

So, after some consideration I took my old shocks to the local Koni importer who offers an inspection service for all of their products – free of charge. And guess what, they were as good as new! After a short chat with the mechanic I decided to keep them and try to find adjustable perches with slightly stiffer springs. It did not take long to find out that Ground Control Suspension Systems in California had what I needed. I was more than happy that a set of Eibach racing springs was included in the kit. I went for 6,6 kg in the front and 4,4 kg in the rear, which the Koni mechanic recommended was a good starting point. Shocks could be revalved afterwards if stiffer springs were needed. I must emphasize that at the Ground Control the quality of the service was as excellent as the quality of the kit – I have nothing but good feedback to give!

While I was waiting for the GC-kit to arrive I made some basic research and measured Miata’s camber gain. Both front and rear were first set to a reasonable suspension height ( 310 mm front and 325 mm rear from the wheel hub center to the fender flare). Then I simply jacked the wheels up while the car was on four jack stands and measured the change of the camber angles. The gain is roughly 0,5 degrees per 10 millimeters of wheel travel, both front and rear.

I could not be happier with these two simple mods. Combined with increased chassis rigidity and more aggressive wheel alignment the car really has started to take corners. I was able to shave of almost two seconds from my best lap time at the first visit to the Ahvenisto racing circuit this spring.

The car feels more planted, steering inputs are more precise, front-rear weight transfer and body roll are reduced and the overall driving experience has become more effortless. This is a good start for the season 2014!

Chassis supports – 2nd measurement

I made a couple of additional measurements motivated by a reader’s comment. Last time in “Chassis supports and door bars – project ready” I used car’s own weight to bend the front and rear downwards. This time I put weight on the door sill and measured the bending that way.

Here are the results:

Weight 70 kg, without door bar. Left: 0,35 mm. Right 0,35 mm.

Weight 70 kg, with door bar: Left: 0,27 mm. Right 0,27 mm.

Weight 100 kg, without door bar. Left: 0,51 mm. Right 0,49 mm.

Weight 100 kg, with door bar: Left: 0,39 mm. Right 0,40 mm.

Conclusion is that door bars reduce bending 18-23 % when measured with 70-100 kg weight. Sounds nice, doesn’t it!

Seriously, deflection with 100 kg is less than half millimeter measured from the height of windscreen frame. Bars seem to work and they give some extra stiffness to old car’s chassis.

More NA POWER part 4: B6ZE cam specs and cam timing

See also the latest post in More NA POWER! Part 5: 100 bhp per liter in 1.7 liter B6ZE

It is hard to find documented data about the effect of cam timing in B6ZE. There are some general rules, though. Solo Miata's Randy Stocker has written in his site that 1.6 liter Miata engine with stock cams benefits from 6-8 deg retardation, if you are looking for max power. Advanced timing gives better torque to mid and lower revs. 

As a general rule increased overlap moves torque into higher revs and decreased overlap gives better torque in lower revs. Explanation is that overlap improves gas exchange in high revs but decreases vacuum in low, which results in lower intake velocity and poor mixing. 

For cams in general, a couple of rules apply. Increased lift increases flow across the power band, but extremely high lifts (1,5 times the original, maby) can make intake velocity to drop in low rpm. Increased duration moves power band higher up at the expense of lower revs.  

B6ZE WITH STOCK, 264/9 AND 272/9 CAMS

So what happens in real life with B6ZE? Here are two examples. Baseline is from Import Tuner Magazine's archives (intake, exhaust and JR cat). Real life examples are from two Finnish private engine builders, both measured at the same dyno. Graphs are in rear wheel figures.  Pay attention, don't concentrate on the numbers! Note how the torque curves look like and where the power starts to drop. 

Nro 1 specs: 79 mm high comp pistons (1.64 liter), 3-angle ground stock valves, mild street porting port matched intake manifold, 4-2-1 header (origin unknown), stock cat, sports exhaust, afm delete, stock 56 mm throttle body and 264deg/9mm Schrick cams (German street and racing cam manufacturer).

Nro 2 specs: 81 mm high comp pistons (1.7 liter), 3-angle ground stock valves, mild street porting, port matched intake manifold, Racing Beat 4-1 header, high flow cat, sports exhaust, afm delete, stock 56 mm throttle body and 272deg/9mm Toda Racing cams (Japanese). 

First I must note, that there is an odd dip in Nro 1’s torque curve. I think that could be sorted with some map and/or intake tuning.

Some observations:

- Schricks start to pull as low as the stock cams

- Torque stays up about 1000 rpm higher with Schricks (measured at a point where still 95% of max torque occurs)

- 95% of max power at 6800 rpm with stocks and and at 7300 rpm with Schricks

- Todas start to show some peakiness, as they start to pull hard from 4000 rpm

- Todas keep torque up until about 7300 rpm (95% rule)

- 95% of max power at 8000 rpm with Todas
- All three engines are running with stock intake manifolds and throttle bodies

- Torque/displacement-comparison shows no significant increase in max torque, but increased flow in high revs pumps power up

SAME CAMS – DIFFERENT TIMING

Here is a demo how timing affects the torque and power. Test was done with engine Nro 2. You can see that increased overlap (from 8 to 26 @ 1 mm) makes higher numbers from mid to high revs. But what really happens here? In theory bigger overlap should give better flow in higher revs. Max power gains are moderate, only about 5 rwhp. Torque gains are significant, but they are in mid revs. Retarded timing was also tested. It slightly dropped torque between 4k and 5,5k, but had no effect in high revs.

Obviously engine has reached its maximum torque, about 140 rwNm, in current setup and flow reaches its limit at 6750-7000 rpm. What happens when intake cam is advanced, in this case 9 degrees, is that dynamic compression increases. Advancing intake means that valves open earlier and also close earlier. Early closing means that there is more cylinder volume to be compressed, thus higher dynamic compression. More compression -> higher thermal efficiency -> more torque.

CAM TIMING CHARTS

Here is a collection of timing charts illustrating different cam timing options. It is easy to see overlap in degrees in circular timing charts. ‘Valve lift versus crank angle’ -charts demonstrates overlap in millimeters. If you find this information useful, please leave a comment!

CONCLUSION

More torque requires more flow. In reasonably tuned hot NA engines practical maximum torque per liter seems to be in 110Nm/l ballpark (in crank figures for 'hot street tune’). High torque in high revs means high power. To keep torque up above 7000rpm is a true test for engine’s, and B6ZE's, breathing abilities. For that, I would suggest, you need unrestricted (preferably tuned) intake and exhaust plus high flowing cylinder head with larger valves and 280 deg or bigger cams.

See also More NA power part 3!