Two weeks of dyno work are behind us after doing a lot of "field tedting" over the past two years.
Thus far we have created base line runs with the stock carbureted engine after optimizing the timing and enrichment. These baseline runs were with variables like air filter swaps, muffler changes and etc.
Here is a pic of the bone stock engine on the RDT labs dyno
Here is our best power with the stock engine with carbs
After phase one of the comparative with our original design for injector location (at the bottom of the intake runner) the HP benefits of the EFI are negligable, with all runs being within 2HP, or the margin of error for my R&D dyno at 1 HP. With EFI the engine runs so much smoother and has more usable torque with about the same powerband with a silky smooth 850 RPM idle speed.
Here is what my Engineer, Tom had to say about the testing over on my Pinz EFI support forum.
Note that the HP figures posted here are SAE, not DIN as the factory numbers and the engine we are testing has a few thousand miles on it- chosen due to the fact that most Pinz that will be seeing our FI kit are also well used and of about the same wear. Internally this engine is a bone stock 2.5
Introduction/ Aims
The overall aim of these tests is to learn more about the Puch engine, its strengths, and weaknesses and how it can be improved. Jake has been performing ‘seat of the pants’ testing during his drive to and from work on a regular basis, using the pinz as his main mode of transport. Now it is time to take it a step further, by getting one of these beasts on the dyno and recording some numbers!
The short term goal is to develop a fuel injection system. The need for which was identified as a direct result of all the miles Jake has put on his truck. Gas mileage, and around town drivability being areas to be looked at to making living with the pinz that much more enjoyable.
In the long term these preliminary tests will help to further understand the very specific requirements of the engine as a whole and allow more new products, services and even full engine combinations to be developed.
My own personal aim with all this is to learn Jake’s method for approaching a completely alien engine and working with it. I feel with all the vw stuff we deal with the story is already half way through, as results have proved so far the challenges are very different here!
To begin, it was important to see where exactly square one was;
Carbs
The engine, kindly on loan from Herbert Krois, was mounted to the dyno, the anticipated problems in this department (these things are VERY different from our staple vw diet!) were overcome without too much hassle. An ‘out of the box’ run gave 77HP@3850 RPM with 127ft-lbs. Stock induction, stock exhaust, 25 degrees of advance. Note, “stock exhaust” consists of the stock headers with the stock muffler bolted onto the flange; not even our dyno room can accommodate the full length pinz exhaust! With Herbert’s help the timing was adjusted back and forth, the ‘sweet spot’ being 28 degrees, 79HP and 128ft-lbs the result.
Next we began to investigate the induction side of the engine. The air filter was removed from the canister, a dyno pull was made. The canister itself was removed, another pull. Finally the piece which joints the two carbs and the air filter canister (which I have christened ‘the snorkel’) was removed and the engine tested. You’ll note I haven’t included numbers from these pulls, the reason being there is no point. None of these seemingly significant changes made the slightest bit of difference, +/- 1 HP at most. We were bemused by all this but not too despondent; who in their right mind would run the mightiest of off roaders with no air filter anyhow? Out came the K&N element. $50 of pure performance. We lost power. We lost more torque. The graphs are presented below and it can be seen that although peak power was up, broadly, across the range it was down. Torque was down all the way around and both curves were more peaky. If you were considering doing this swap in isolation, I’d save the $50.
Finally for our tests with carbs exhaust came under scrutiny. In Jakes experience this is probably the biggest area of performance improvement to be found in vw engines. The pinz has a set of merged headers as stock, sort of. Two pairs of cylinders merge into one pipe at an all to acute angle, and the two remaining pipes never merge, but empty into the stock muffler and exit as one. The first test was with no muffler. Yes, it was loud. No, no one would ever run like this, but what if? We were back to the 76 – 77HP we initially saw. Strange, we were expecting much less, in the way that ‘dual cannon’ buggy pipes kill vw power. Next up for testing was a fully merged exhaust, with a trusty Magnaflow muffler. The full merge was achieved using a pipe provided be Herbert which bolted onto the stock header flange and Y’ed into one. This provided some extra length to the system as a whole and gave a 4-2-1 style exhaust, big torquers in the vw world. Torque fell, well stumbled, to 125ft-lbs, HP was up with 79@ 3850RPM being the new high score. No time to head scratch over that one, out came the K&N element. Drum roll please… 83HP! Jake had seen this happen before, and it stands to reason, if air can exit easier more can get in to replace it.
This was as far as Jake wanted to go with carbs. Off they came, and on went Herbert’s plenum and a RAT supplied SDS engine management system with direct fire ignition. The stock air filter canister and element and exhaust were refitted.
EFI
Timing was easy to perfect, having the factory literature (thanks again Herbert) the advance curve could be copied, and modified in accordance to what we had gleaned from the testing with carbs. Again the sequence was repeated, stock air filter, no air filter, K&N. Peak HP in all cases was 80, +/-0.2, immediately pegged to the best of the carb’ed runs also with the stock muffler. With this system the K&N showed its worth a little; note how similar its graph is to the graph with no air filter. The stock air filter made the same peak HP, but with a narrower range. The stock filter made more torque over a wider range, particularly down low. I think I’d still save my $50.
Tomorrow brings further EFI testing, with the exhaust swap being first up, followed by changing the position of the injectors. Jake would like to stress that the pictures shown are of Herbert’s current set up, with the injectors below the fan cowling. The plenums RAT will produce will have the injectors above the cowling, on safety/litigation grounds. We have injectors already mounted up high but not connected in this test plenum, as shown in the photos. We expect to see some differences in output (or maybe not
) from this change.Conclusions (So Far)
There were some clever people at the S-D-P factory! This is an almost perfectly evolved beast for its intended purpose; to hum along at 3500RPM gobbling up the terrain with masses of torque (compared to its horsepower output). The engine is aircraft-like in its power characteristics, it makes a set amount of power and torque and will operate at that level until the cows come home. With VWs bolt on trinkets make big changes, Not so here. 4HP is the biggest change we have seen over stock so far, from changing both intake and exhaust. In terms of HP/Effort that’s not good. There is a limiting factor with this engine and it is internal; cam or valve sizes or port work (or all three) are required to really impact overall output.
We’ve also seen that to alter the pinz’ evolutionary course; to make the pinz a usable civilian vehicle, EFI is a viable option. Low down grunt is boosted and higher in the rev range power is maintained (limited) at factory level. This torque boost will help drivability as well as off road performance. Fuel consumption, another of our concerns is far better. Although road testing is the only way to get a definitive MPG number comparison, a full tank on our dyno lasted approximately twice as long with EFI compared with carbs. Another benefit was a cooler running engine. The pinz engine is not know for running hot, and so head temps were not recorded, however the oil took noticeably longer to reach operating temperature than when the engine was carbureted. Improved cooling in the pinz’ new role of commuter vehicle (sitting in jams, and slow moving town traffic) cannot hurt and any cold start issues can be dialed out via enrichments in the ECU programming. Jake says he sees this type of temperature phenomena on a regular basis on engine combinations identical apart from the fuel delivery method.
Interesting stuff, more to come,
Tom
Here is a pic of the test engine being tested with plenum #1 and injector position # 1 for comparative analysis of plenum sizing and design as well as injector placement to be compared with the field testing I have been doing for almost 2 years.
THIS IS NOT THE PLENUM WE WILL BE USING WITH OUR KIT!!! It was "borrowed" for this comparative test only! What you can't see are the injectors lurking under the cooling tin!!! Neither of these are the way we plan on doing the kits, this has only been done to attain comparative data from all possible injector locations and plenum designs.
Do not the total lack of the distributor and the super trick mount we have devised for the dual purpose job of mounting the hall effect sensor, blocking off the dizzy hole and mounting the coil packs.
This has been very intense and we still have at least anopther month of comparative work ahead of us!
