Expert: Dan Liddy - 3/27/2011

Question
Hi, i recently purchased a 1998 nissan sentra sti modified for club racing at our local track.I used to race superbikes and find
myself in unknown territory. Problem is the gearbox keeps on braking 3rd, 4 th gear depending on boost.Currently the little nissan gets its power from a sr20 det with a sr16 limited slip  gearbox, garret turbo t62 and i have noticed it uses a tilton three plate clutch
and a massive overweight flywheel. Upon my question on the weight, the previous owner told me he wanted more torque, i believe this could be a mayor contributing factor to the stripped gears? not sure? i remember from the bikes we always tried to
get the parts as light as possible so it can rev harder, not sure if it applies on cars? The race category is open and the nissan
must perform againts modern cars like the focus rs and opel opc cars. It is fast, but reliability seems to be an issue.
The boost is set at 1 bar psi, even with coilovers it still spin in third and fourth, should i turn the boost down? or could the heavy (double plus flywheel or tilton non slip clutch) be the problem?
What would you suggest i do to get it more reliable, the engine has never given any troubles,and for a front wheel drive car it really goes well around the track, but i can not spend loads of money after each event, it is not fun anymore.

Answer
Hi Donald:
I'm not sure what's causing your problem with 3rd. & 4th. gears, but I think if you send new ones out and have them hardened more, it may solve the problem.

You'll have to do some research first, I haven't run into this sort of trouble in years. Then the trouble was a poor design, I doubt that's the case with your Nissan.

In the mneantime, if you think dialing back your boost will ease the strain, try that. Also, you might wish to analyze your driving techniques to see if your style is over stressing the gearbox.

I am not sure if the heavy flywheel could be causing the breakinge, but I don[t see how. lighten it anyway, it does nothing to improve torque.

Best of luck

Dan Liddy
Sarasota, Florida