Decompression turbo plates
Discussion
On the Bay at the moment there is a Decomp plate for sale so I would like to pose a questions please.
I have an HSK turbo fitted backed up with a Saab intercooler and Aquamist water injection plus an oil cooler ready to fit.
Cars clutch feels on the limit and I estimate approx 170 bhp on a 1.6 with original high compression engine which is healthy.
If the plate is fitted would the power go up much?
I get the idea that most good turbo cars lower the comp to get more mixture in.
I guess these questions are aimed mainly at mr Lazza who seems to have the knowledge.
I have an HSK turbo fitted backed up with a Saab intercooler and Aquamist water injection plus an oil cooler ready to fit.
Cars clutch feels on the limit and I estimate approx 170 bhp on a 1.6 with original high compression engine which is healthy.
If the plate is fitted would the power go up much?
I get the idea that most good turbo cars lower the comp to get more mixture in.
I guess these questions are aimed mainly at mr Lazza who seems to have the knowledge.
AKA a thicker headgasket.
Terrible idea, you ruin the squish area, and add more hotspots, thereby increasing the propensity to knock.
Reducing the compression ratio will also reduce off boost responsiveness and drivability.
Save the money you'd spend on it and fitting and purchase good engine management and a new clutch. You're no-where near the limit of the stock engines capabilities.
if you're also using Water Injection, you've little to worry about with knock - assuming it's tuned appropriately.
The MX5 engine is not exactly high compression to begin with anyway.
EDIT: Just adding this decompression plate even optimistically speaking wouldn't directly increase power, it'd reduce it.
Terrible idea, you ruin the squish area, and add more hotspots, thereby increasing the propensity to knock.
Reducing the compression ratio will also reduce off boost responsiveness and drivability.
Save the money you'd spend on it and fitting and purchase good engine management and a new clutch. You're no-where near the limit of the stock engines capabilities.
if you're also using Water Injection, you've little to worry about with knock - assuming it's tuned appropriately.
The MX5 engine is not exactly high compression to begin with anyway.
EDIT: Just adding this decompression plate even optimistically speaking wouldn't directly increase power, it'd reduce it.
Edited by Richyvrlimited on Thursday 13th November 11:13
Absolutely not needed, and your simply creating work and potential for buggering something up.
The 1.6 BP is plenty low enough compression to run a lot more power than that.
What engine management are you using? As that, really, is the key to more power.
The basic internals are good for well over 200hp, generally torque limited as you the rods are first thing to give up.
The 1.6 BP is plenty low enough compression to run a lot more power than that.
What engine management are you using? As that, really, is the key to more power.
The basic internals are good for well over 200hp, generally torque limited as you the rods are first thing to give up.
Enough said 
In theory, with lower compression you would be able to increase the boost and advance the timing which is where the additional power would come from but as Richy says, it's not as straightforward as that.
Higher compression gives more power like for like anyway. My SC only runs at around 8psi yet I get over 240bhp. Comp ratio on Mk2.5 is 10.5-1 compared to about 9-1 on Mk1. Of course the flow rate of the MP62 helps here too...
In theory, with lower compression you would be able to increase the boost and advance the timing which is where the additional power would come from but as Richy says, it's not as straightforward as that.
Higher compression gives more power like for like anyway. My SC only runs at around 8psi yet I get over 240bhp. Comp ratio on Mk2.5 is 10.5-1 compared to about 9-1 on Mk1. Of course the flow rate of the MP62 helps here too...
Thank you gentlemen, as you can see I am new to this blown business, but I like it!
The engine uses standard management but HSK supply a piggy back unit that plugs into the ECU (when getting the car through IVA it was clear that it certainly changes the fueling as the standard ECU runs it far too lean.
My worries are just to keep it cool then as I will not track it till I am happy that it stays in limits.
I have to admit that I dont want a car that has nothing and then comes on with a bang.
Thanks again.
Jon
The engine uses standard management but HSK supply a piggy back unit that plugs into the ECU (when getting the car through IVA it was clear that it certainly changes the fueling as the standard ECU runs it far too lean.
My worries are just to keep it cool then as I will not track it till I am happy that it stays in limits.
I have to admit that I dont want a car that has nothing and then comes on with a bang.
Thanks again.
Jon
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