Date: Mon, 20 Dec 1999 19:45:50 -0000 From: "Alan Buckingham" <alanbnopsamb.swinternet.co.uk> Subject: Classic900s - 8v vs 16v performance results
To kill some time last night I got together as many old road tests as possible for the classic 900 turbo ranging from 1978-1989 (including one 99 turbo). I then put as much of the performance data as possible into Excel and did some comparisons. Clearly one needs to be cautious in comparing results because of variations in drivers and conditions. However, findings are as follows: Cars tested: one 99 turbo, three 900 turbos without APC, three early '80s 900s 8valves with APC, one 1985 900s 8valve turbo intercooled, one 1984 900 turbo 16 valve, one 1984 900 turbo 16 valve 's' (Aero), one 1989 900 16v Carlsson. 1. There is no overall pattern unlike one would expect. I expected the earliest cars without intercoolers to be the slowest and the 16 valves to be the quickest but this wasn't true. For example, the quickest car in the 0-100 dash is a 1983 APC 900. Smack in the middle of the bunch is the '185 BHP' Carlsson just in front of the 99turbo! Regarding the other two 90016vs, one was one of the fastest and one was one of the slowest in the group. 2. I tried to factor in kerb weight and number of doors but this made no difference to the results. 3. There is, however, a pattern to in gear acceleration times. The 900APCs (esp. the intercooled one) have much better acceleration characteristics from low speed in 4th and 5th gear than the other cars (including 16vs). For example, 30-50mph in 4th gear: fastest 900APC = 6.8 secs, 90016v Aero = 8 secs, 90016v = 9.4 secs. However, from 40-60mph onwards the 16vs take over e.g. 70-90mph in 4th: 16v Aero = 7.3 secs, all 8vs in the range 8.6-9.2 secs. The story is exactly the same in 5th gear. 4. Some of you will be thinking that the reason why the 16vs are slower initially is because they run higher gearing. Well, I controlled for this as best I could and still the differences remained. The 8vs (especially the intercooled one) were the quickest initially. However, they were eventually overtaken by the 16vs as the speeds rose. Conclusion: The most striking finding is that there is great variation in performance for seemingly identical cars. There are a number of possible explanations: 1. There was a great deal of variation in the testers (but driver difference should be less obvious once past 70 mph when doing the 0-100 dash or doing the in-gear runs), 2. there was a great deal of variation in weather conditions (yes, temps did vary a bit but all tests were conducted in the dry), 3. they were run on different octane fuels (well, all tests were in the UK pre-1990 and before unleaded had become popular, so I presume similar octane fuel would have been used) 4. Saab let allegedly identical cars out of the factory with very different BHPs. I prefer the latter explanation. Perhaps some of the Saab factory workers were a bit liberal with their adjustment of the APC potentiometers when they installed them! The second finding is that the extra 20-30bhp of the 16vs seems to count for very little. 16vs may be more refined but they seem to lack low down punch (does anyone have a graph showing the torque curve of 16vs versus 8vs?). This is a common characteristic of cars with 18 valves. Therefore for everyday driving an 8v with the boost turned up a bit is going to be a better mover than a 16v. Alan 1989 900turbo (8 valve, intercooled and with boost wacked right up).
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