mx5cartalk.com

Hi people, I was on the verge of buying a SP until I heard from a reliable source that it is reasonably common for the rods to end up out the side of the block. I have even heard that this has happened with cars running standard boost.

I finally made my decision (and yes it has been agonising) to go for a SP over an SE to produce a daily driver oriented towards a track car (meaning I will aim for about 160 - 180 rwkw with suspension lsd, etc) but now am having second thoughts about an SP at all.

I am very interested to hear from SP owners (THIS IS NOT AN EXCUSE TO CONTINUE THE SP vs SE DEBATE) about this. I cant afford to pay for a rebuild so putting in stonger rods, pistons is not an option for me.

Help!! I have had a gutful on trying to decide

None of the SP race cars have managed to ventilate their blocks yet. They are having other driveline problems though, like gearbox's and diffs. It sounds like 180ish kw is about the limit for the NB8B driveline in race applications.

Actually, does anyone have any first hand experience with SP's with broken rods? I haven't heard of any.

The rods out the block happened in street dríven cars so I was told. I know of at least 3 Sp's this has happened to....3 out of 100 3%.

Basically I need convincing this is very rare and not to worry, otherwise SE.

Never heard of it. I have heard of a high boosted silver NB that did this though, but not an SP.

Jules

Well I have over 100,000km on my car and my boost has been a little higher than stock for about 80,000km and my block is still in one piece and not burning any oil so I'm pretty happy. My turbo isn't happy though. It's getting replaced next week. (thanks Brian)

I suspect this is a myth Yarn. Haven't heard of anyone with this problem, and if someone has ventilated the block on an SP it would most likely be from abusive driving, over revving on a downshift being the most likely way to achieve this (changing from 5th to 2nd instead of 4th might do it). That would have nothing to do with the car or its design, only the driver. Mine is on 106000 km with no problems at all, and Dave's car is much higher mileage than mine with greatly increased boost - no problems there either. If there was a tendancy for this to happen to SPs then people on this forum would be well aware of it ...

Well, I definitely know that this is not a myth, but it is good to hear that it may be isolated. I mean, turboed NB's are basically an SP anyway. Now I am really confused. Bigdog, are you running standard boost? and ECU?

Anyone with servicing experience come across this??

Mine is stock plus hose mod. By 'myth' I meant that this is atributed to the SP as a fault. I have no doubt that some one has managed to throw a rod, but the same could be said for almost any car model. Doesn't mean there is any weakness in the design though.

Similar failure was mentioned in a previous post but it wasnt a SP:

http://www.aus-cartalk.com/viewtopic.php?t=22376&highlight=avo

Never heard of it... I have heard of one vehicle having excessive amounts of blow-by, but generally, nothing to do with rods letting go.

I've had my SP from new, and anyone that knows me can attest that I don't always treat my car gently.
In fact, it redlines at least once every time I drive it.

My car has done a fair bit of track work and various driver training days, including drift lessons sitting on the rev limiter, and my engine is still 100%.
Not long ago, I had some more engine work done, inclusing increasing the boost to around 12lbs, and it still goes strong.
Quite a bit stronger than stock actually.

I have heard of 1 SP that did throw a rod out of the block, but that car was being fitted with a new computer, and was running on a dyno at full noise, when the mixture went lean and the engine raced and I believe it was revving at close to 9K when the rod let go.
Not something that you could do to a normal SP.

I know of another NB which was turboed, and on it's first drive, one of the injectors was stuck full open and flooded the cylinder leading to hydraulic lock which broke a rod.

Really, the SP's are pretty bullet proof, and if you brought an SE up to the same performance, you would be running the same risk of putting a rod through the block, which is highly unlikely.

Buy the SP, and live happily ever after.

Well, you've just explained two of them right there Benny!

Yarn, if you can get your hands on an SP that you're happy with and has been maintained, go for it!

I also have never heard of it happening.

Boags

I'm not an SP owner, but know a few, mostly making about 140kW in daily drivers and weekend warriors. No sign of this having happened to any of them. Also no reports from forum members (probably about 10 SPs here, many of them seeing light track duty from time to time).

Cheers,
Alf

Yep - never heard of it either.

As has been mentioned here, its revs that normally do rods in. Pretty much the only way you can over-rev a modern engine is by muffing a gear shift and driving the engine over the rev limit through the wheels. Unless you flood it with fuel or water of course.

If it was a boost/detonation/fueling issue then the pistons would be the victim, and the rods might go if everything comes to a sudden stop.