paulob1 said:
pum noob thanks for that, my thought process was that with 250 maybe 300 bhp on tap I will be spinning my wheels. My biggest worry was wheel bearing and suspension unit failure...get your point about the effort but the bigger wheels will only conpensate for taller gearing and fitting a heavier clutch has to be a major issue anyway...
I would have thought bigger wheels, bigger brakes better stopping. Give me more of your thoughts on this...
Wheel bearings wont be affected by power, they will only be affected by wheel size, camber, and how you drive the car, so i wouldnt really worry about that. The same goes for the suspension, it will only be affected by adding weight to the car, widening the track significantly, and how you drive the car, so if you get a good set of suspension, it wont be under any extra stress then a car with less power.
With regards to wheel size, shorter gearing will help with the slower acceleration, and clutch slipping, but not with stress on thgearbox and driveshafts. regardless of gearing, a smaller circumference wheel on the same engine set up will always be less stress on the driveshafts, clutch, and engine, and acceleration will be quicker, providing you can put the power down! Im pretty confident that if you produce more then 200ftlbs, a standard 1.7 or even FRP box wont cope for long if you are going to drive it hard, although i really hope you prove me wrong!! An FRP box only has shot peened 1st and 2nd, the rest of the box is exactly the same, other then shorter gearing. The bearings are the same, and the strength of the parts are the same. This is one of the reasons ive not gone any further with my 1.7 turbo, because buying uprated gearbox internals just seemed very expensive for where i was going with that car. I also think if you are going to be looking for 250 upwards, depending on torque, you might need a very expensive twin plate clutch, i struggled to find a clutch that would take my power, and thats without an LSD and with very small wheels! With 17" or 18" wheels, and an LSD, you will be putting a hell of a lot more stress on the clutch.
I agree totally with the bigger brakes though, the bigger the brakes, the better, depending on pad compounds and disc material ect, but like for like, bigger is better. The only issue i have come across with bigger brakes is disc weight, but you can overcome that with lighter rotors and alloy bells.
There are a few different sized housings for a T25, but the average T25 wouldnt sustain 15psi up to redline on your engine, but it depends on cam lift and timing too. If you have very low duration cams, and low lift, you would sustain 15psi, but thats not a good thing. You shoouldnt really look at boost as a power indicator, i know its the easiest way to express boost, but psi is just restriction! You can have 2 engines both running 10psi of boost, but one has 100bhp, and the other has 200bhp. The more efficient an engine is, the less the boost will sustain from an identical turbo. Boost is only gas that the head is unable to flow. If you are using a journal bearing turbo, then the average T25 will struggle to make any more then 250bhp on your engine. The turbo can not flow the required gas that needs to go through your engine to make that power. There are of course exceptions. A ball bearing turbo will easily flow enough, but you'd need to make sure you had the supporting mods. Once a turbo goes past its efficiency range, it will blow hot air, and the faster the velocity of the air, the less efficient an intercooler becomes! So you can actually loose power if you try to run too much boost.
With regards to Megasquirt, you said you are getting somebody else to do the work on your car?? If so, then id reccomend you dont use megasquirt, and go with OMEX or Emerald. Megasquirt is a very good ECU, just as good as the others in its class in my opinion, but its still a homebrew ecu. Its ideal for DIY builds, im using one myself, but there is not support phone line or email address you can contact if your struggling. There are a lot of different settings, setups, ecu types, board types, and versions. It has one of the biggest DIY support networks, but a mechanic cant rely on browsing internet forums to get answers, and as a result, a lot wont touch it. With OMEX or Emerald, you can get on the phone and have answers immediately in most cases. The customer service for OMEX is second to none! Once the megasquirt is set up properly, it will run just as well as the others, so just take this all in to consideration and do your research before you make your decision.
I know you might already know most of what ive wrote, but its just a few things that might be useful if youve not given them any thought, they are just my opinions, so others may not agree fully!
