a TDI engine you can buy today would have almost DOUBLE the HP (170 vs. 90) from the factory with only a 0.1L increase in displacement, and in modified form be an eyeshot from making 280 HP/400 lb.ft. An IDI would be very hard pressed to reliably match this. 400 lb.ft. with a 22.5:1 compression ratio,
That TDI you speak of is a 16v with improved airflow. Comparing 16v to 8v is apples to oranges. It is not available in NA either. Anyway, to keep the IDI vs. TDI discussion consistent, perhaps it would be better to keep it 8v?
You mentioned daily performance/practicality. 400lb-ft will require a fairly stiff clutch that could reduce traffic/daily driving comfort. The general drivetrain reliability or FWD traction with street tires may also be a concern. A comparible TDI with VE pump and 8v with 200whp is extremely rare here, although we've seen a handful of 170whp 350wtq examples. There hasn't been an IDI with proven 200whp either.. I don't think VW diesel tuning became very popular until the TDI days so there's only a small group of us still tinkering with IDI.
Especially in TDIs, it is easy to have too much torque and not enough HP. An IDI's powerband with peak torque between 4,000 to 5,000 RPM may arguably be more usable in a FWD vehicle used on street and on the track.
The turbo setup used in my 1.6L IDI is in fact the Upsolute Stage III marketed towards TDIs. On a TDI it supposedly dynoed approx. 170whp. With no intercooling, stock cam, and a basically stock block, my 1.6L in a fully loaded 1997 Golf managed to outperform a MK3 VR6 (172hp/155whp). I haven't raced any 170whp-plus vehicles. I also had wheelspin near 4,000 RPM in 3rd on dry, level road, albeit with all-season tires. Unlike the TDI version with the same turbo kit, My IDI had
zero smoke in the entire RPM range, with a 9mm pump head and stock injectors. Yes, stock injectors. I don't have hard data like a timeslip as I haven't gone to a track during Winter, but the personal experience left me thrilled.
My next pump update will include a 12mm. Custom fuel injector nozzles were recently acquired from Dieselicous. I am very concerned about the 12mm's RPM limitation, but Superior Fuel said they have some tricks so we'll see. I'm going to have 10mm or 11mm standby just in case.
After the pump's IQ was cranked up to the max, I finally had some WOT smoke below 3,000 RPM. Peak torque was 4,000 RPM. The camplate in the pump started floating at around that RPM, resulting in gradual fuel loss and the torque peak stopped rising.
In case you're wondering, no the 1.6L with the GT20 turbo wasn't sluggish at all during low RPM. It had more get-go than a VW 2.0L 8v gas engine. The GT20 turned out to be too small with too much backpressure. A nice daily driver turbo, but it doesn't suit my max. HP goal. You probably saw the early picture of compound turbos that 935racer set up.
Last fall, my brand new IDI's compression was so low that the engine could not idle on its own unless I revved it and put load on the engine for a minute. The engine still fired up after the 1st crank though, even with a small gas starter motor.
After about 4K or 6K miles and switching from a 3-hole to a 1-hole headgasket, the engine was able to idle on its own during cold start in Winter. I went to Aircare and passed with 2.##% exhaust opacity, below the average passing diesels and well below the 30% limit.
I wonder how much ceramic coating the head will improve cold starts, anyway I daily drove the car at minimum 1 hour 30 minutes each day. I think at that compression (likely in the 350's, below the 412 wear limit) the engine can still handle a lot more power, we'll see.
Heck, very low compression probably isn't needed if I only want to make 211 wheel torque at 5,000 RPM for 200whp. PCP shouldn't be a big concern then, and it'd still do perfectly fine for daily driving.
The wall for IDI performance still remains to be seen :?:
Topic: IDI engine, there IS a future... (Read 83347 times)
