The options for engine upgrades, either supercharged of turbocharged, for our Elises/Exiges are growing fast! Which is a very good thing, but it also makes keeping an overview of all the various upgrades harder. Therefore I made a table in Excel (first picture below the text-body), based on the excellent list made by JasonD in post #52 in
Forcefed Turbo vs. Sector 111 blower??? - Page 2 - LotusTalk - The Lotus Cars Community.
I added some other possible engine upgrades to this list, tried to include prices for as far I could find them and included the internet links where I found the various WHP/ft-lbs numbers. The list is not intended to list all possible upgrades, I try to limit the table to the more commonly used upgrades.
Based on the useful comments in post #2 from CharlieX (thanks for that, Charlie), I added additional data into the overview for the estimated average ft-lbs during racing on the track (
defined as 5500rpm-8000rpm) instead of only using the peak ft-lbs figures. The reason for using the average for the 5500rpm-8000rpm area is that basically the idea is you mostly are in this area on the track.
Using the overview, I made the following graphs (we humans are visual oriented animals, also the reason why we bought our cars) for the Elise (for Exige: see post #8) to make the interpretation of the figures easier:
Graph 1: WHP / ft-lbs (peak)-graph. Creates insight in how much power the upgrades make in both WHP and ft-lbs (peak).
The upper right corner is where you want go for maximum power.
Graph 2: WHP / ft-lbs (average race)-graph. Same type of graph as graph 1, only using average race ft-lbs instead of peak-lbs.
Graph 3: Costs per extra WHP / ft-lbs (peak)-graph. Creates insight in how much US$ each additional WHP and ft-lbs will cost you.
The lower left corner is where you wanna go for lowest price per additional WHP and ft-lbs.
Graph 4: Costs per extra WHP / ft-lbs (average race)-graph . Same type of graph as graph 3, only using average race ft-lbs instead of peak-lbs.
Please mind:
1. Re Graph 1&3: these are peak figures only, it may/may not say much about the underlying curve. See also post #2 underneath from CharlieX.
2. I made various assumptions, mostly regarding pricing, please see spreadsheet for further details.
3. I'm not a mechanic, I have no idea re streetability and durability.
4. In the graphs 2. and 4. I didn't alter the WHP-figures (yet), because it's my understanding these basically are the result of the torque.
Conclusions:
- Re two lower cost 1st Gen SC kits (BWR & S111): the BWR Stage I appears to have a slightly better bang for the buck that the S111 Katana.
- Both 1st Gen SC kits when compared to the 2nd gen SC kits (VF SC kits with intercooler and the BOE TVS SC) get their asses kicked in terms of power output and also, to a lesser extent, in the $ you’ll need to cough up per extra WHP and ft-lbs. So if you have the extra money for it: it makes sense to buy a 2nd gen SC kits: more power and higher bang per buck.
- Although the BOE TVS SC and VF lead the pack in terms of WHP and ft-lbs, also the costs are a bit higher because fuel pumps and upgraded clutches are required. Both BOE and VF Stage II still have, although is pretty minimal, a slight lead over the VF stage I in terms of $ per extra WHP and ft-lbs. Please note that if you install it yourself and therefore avoid the installation costs of the clutch and fuel pump, both the BOE TVS SC and VF stage II take a much bigger lead over the VF stage I. Open the spreadsheet in post #10 if you want to see the graphs based on the cost excl. labor.
- The influence of changing the ft-lbs (peak) figures into ft-lbs (average) figures is almost nil. I.e. all kits lose approx. the same % when peak ft-lbs is adjusted into average race ft-lbs. Exceptions are the:
FF275 kit: has a lot of torque already in the lower RPMs but loses ft-lbs when ft-lbs peak is adjusted into ft-lbs average race.
VF Stage I : which almost doesn't lose any power when ft-lbs peak is adjusted into ft-lbs average race.
One last note: see my post #47 for a remark re comparability of the kits: the BOE TVS kit now includes a A/F meter and tuneable EFI ECU, both components not present in any of the other kits. If you value these components then the graphs don't tell the whole story anymore. See post #47 for further explanations.
I hope you guys find it handy in weighing your upgrade options! If you have any questions or suggestions to add other upgrades (including ref's), don't hesitate to post! You can find the file of the spreadsheet in post #9 for further abuse.
Thanks Enrico