Bosch pumps = crap. I've been through about 3 and am just sticking with the Toyota one now. It's got the best flows necessary and you can rebuild it. Bosch etc fail on both those counts.
I've just emailed Cory a few of my thoughts and here they are....
Hi Cory,
From the research I've done in the past the estimated limits for the 185 RC WTA and 205 WTA are approx. 350BHP and 400BHP respectively. These figures were quoted by an ex-TTE guy.
Obviously, without restrictors, the Group A cars would have been pushing approx 500BHP and based on the fact they used water injection and race gas you can probably get a bit more from them by using water injection too. I do and everything seems quite happy. I may be looking into fitting a restrictor to my car at some point, with a tailored, compressor as this can help to improve torque due to the benefit of the restrictor actually speeding up the air through the bellmouth.
A larger heat exchanger will not do any harm esp. on 165/185 WTA systems and good insulating of the core on the underside should always be done. The restricting factor to the system is not it's ability to shed heat, which it does very well, but the fact the charge air does not spend a lot of time actually in the core so there are limits to how much the air can be cooled unless you use an ice reservoir and that's really more suited to a drag car than a daily driver. In the summer upping the coolant capacity with a reservoir can help slow down the overall heating rate of the system. Depends on the summer temps in your area. I think the TTE guys used approx. a 20L tank in the boot for the Safari rally. Nial on the OC actually had a custom top mount WTA core made and has found that has had an effect on the overall temps due to a larger surface area available to the airflow but nothing really dramatic,esp for the time/cash involved, so a good 205 setup really is a good way to go. I don't think Nial is looking to put his WTA into production and it looks a bit agricultural too. On my car I have dual 9" SPAL fans and run the pump constantly so that there is no heat soak at any speeds including sat at standstill.
If you do upgrade to a better rad an Audi 100 radiator can make a good upgrade. Make sure you look for the type with the inlet/outlet at the same end though for ease of fitting.
The Toyota pump is the best out there end of story. The same pump was used on the Group A cars and is relatively easily rebuilable as long as you remember the impeller nut is a reverse thread. I didn't first time around!!! Doh doh doh!! Nothing a bit of work on a milling machine can't sort out though.
The Group A cars used a swirl pot at the highest point. Can be useful to bleed the system but not really necessary.
If you have a A/A185 now you can fit a CC under the bonnet but make sure you remove all the metal parts under the hood scoop as it can rub the core/possibly cause a leak. You would be better off with an RC/CS bonnet/bumper though.
If you fit one with the old bumper in place you can just about get a Fiat Cinquecento radiator in there as a pre-rad as the MR2 guys do. Might take a bit of work with A/C.
Also you can fit a 205 core straight on with the throttle body adapter off a 205. Takes a bit of work but nothing too major. Some people cut/reweld the turbo inlet pipe so the core sits straight but it doesn't need to if you make some brackets.
If you do look to fit a standalone ECU in the future the mapper will thank you for having a WTA system as, generally, you won't get temps as low as a FMIC in some instances but the temps during pulls are solid and repeatable rather than varying a lot which can happen with an FMIC. It's the water's ability to absorb heat spikes that helps. This morning we had an ambient of 12/13°C and once upto highway cruising speeds the intake temps sat at around 22/23°C. Under boost temps would not rise above 30°C.
I've tried to put most of my thoughts down here but if there is anything else you'd like to know just ask and ill try to help.
Cheers
John