Megasquirt system

[Leesfer]

How much of a performance boost will changing from the Bosch fi to a megasquirt system be? Is there a noticeble difference? Is it remappable? And how much money are we looking at?

[racydave]

What I can tell you is basically what I have read. And it depends if a marginal gain in performance will make you happy. You also not only need to be a fairly good tech to do the rigging, then you would need to borrow or write a "map". Also youll be tempted to go with larger injectors. Id also wanna control my ignition, you loose alot going thru the belt, camshaft and dizzy, modern cars have cranksensors.

[So Cal Mark]

I don't see a benefit with a stock engine

[Leesfer]

The engine wont be stock...

performance cams, free flow exhaust, free flow cold air intake and filter, 8.9.1 pistons

[So Cal Mark]

well, that changes things quite abit.

[bandit]

The TB on the stock manifold is to small to gain much performance even running modern ECU and Mods on the Engine
if you can't feed it more Air and Fuel you'll be wasting your time .



Daniel

[brad131a4]

From what I've read the stock tb and manifold on the spider has a flow capable of handling up to 250hp. Now if you are just n/a then you can get a better driving car as you can fine tune the air/fuel ratio to its optimal ratio and flatten out some of the ruff spots on the torque and hp curves. Will you see a huge difference probably not but you will feel a more responsive car with a better power band and smoother power output.Which to me makes it a better driving experience which would lead me to believe that it would be a good thing to do.

[bandit]

Dont believe everything you read brad, i have a modified FI 2L with a few mods on fi and engine no where close to
200hp let alone 250 . The TB and manifold of a FI spider can't flow that much take a look at the size of the VTec
hondas TB closer to 60 mm if i remember correctly .


Daniel

[pope]

There is a big misconception here. There is a conception that the more air you can get to an engine, the faster is will go. Yes, to a point. And the point is the maximum amount of air an engine can handle. That number is determined by the Cubic Inch Display of the engine. The 2.0 (122cid) stock Fiat Spider's maximum need for air is 211 cfm, reguardless of cam, valve, injectors, headers, pistons. That is the maximum amount of air the engine could ever use being naturally aspirated @ redline. The stock spider engine as built with no upgrades, uses only 168 cfm. The 55mm throttle body can produce 317cfm. Well more than the engine can use. As an engine builder, you must figure out how to put components (valves, porting, manifolds, exhaust, cams, and lets not forget fuel and compression ratio) in that will get you to as close to 211cfm as possible. 211 is a pie in the sky number, you'll never get there, but, thats the challange. 317cfm for the throttle body is a static number in that it will always stay the same. For instance, you need 194 cfm to produce 200hp on that engine.

The other way to increase the limits of what the engine can produce on its own is to jam air into it, by using a Super or turbo. They force more air in causing a higher compression of air than the piston can do on their own.

Dont blame the throttle body, look every where else first.


Brad131a4...you're correct in that the throttle body is capable of supporting close to 250 hp. I am just talking of naturally aspirated engine. The rest of the engine is not though. You would have to increase the piston diameter to make the engine a larger cubic inch engine and lots of other things. But again, the throttle is not the problem.

[Leesfer]

I've heard people talk about different fi upgrades, what kinds of options are there to upgrade the fi system? Or is it even worth it or necessary?

[racydave]

"Tuning" a engine to me is the chase of the weak point in the flow, and a plan of attack. What are the desired results? If a engine has 100 HP, what would you give for 110? Id also welcome improvments in the driving experirnce. I dont have to keep up alot of revs to still have good power. If I could afford it, I think to optimise a 2L, I would do the system ( M-jolt ) with a cranksensor and ign system. Id have med size headers with no cat (Keep the low end torque ). Id have the heads ported and polished. Id probably check into cams and adj cam wheels. How bout a slight boost in compression? Will I have to bore the block? Maybee the compression ratio is ok where it is... But now, the fun starts, as you get to fine tune the fuel and ign systems! Id love to achieve most of this on my 36 ADL naturally aspirated with crank sensor ign system. Just got some headers today!

[bandit]

Brad131a4...you're correct in that the throttle body is capable of supporting close to 250 hp. I am just talking of naturally aspirated engine. The rest of the engine is not though. You would have to increase the piston diameter to make the engine a larger cubic inch engine and lots of other things. But again, the throttle is not the problem.

When i wrote about the TB i was really referring to the System as a whole I completely understand what
pope is saying here and to break it down a little more the Air Flow Sensor is the weakest link and liming factor
(cfm) . It is always interesting to get other view points about these Cars but i haven't seen very
many people try to Mod the FI what I've seen is some switch to Mega or Haltech . Others have used the FI to
feed custom Turbo setups . What i have done to mine was Larger Cam's 8.9 Pistons Ported the head and
Manifold, ported the opening of the TB, Header and free flow Exhaust, K&N Air Cleaner . The cars runs well
i am happy with a reliable Fiat that starts right up and has maybe 130hp .
From a practical point of view i agree with Mark that spending money on the FI with a stock Engine
would be a waist but i know how we want more power then stock as well . I have built race, street
performance, and stock TCs and to get a big gain costs some good money and if you try and skip
this or that or spend good money on FI but not go through the Engine and Exhaust you'll be waisting
your time and money .

The Best bolt on improvement i've ever felt without going to an extreme was dual carbs IDFs or
Side Draft you pick up a good 20 to 30 HP from a single Carb Engine but before i get knocked
here i'll say this the Dual Carbs would be a much better up grade with Cams higher CR Pistons
Header and Exhaust !

Hi Pope
Just wondering where your getting these figs from ?
About the 211 cfm being the maximum flow for Fiat 2L i would disagree with that fig . The the most
hp I've seen someone get from a 2L was 230hp Asp. but this is a full race engine not what most people here
would be interested in .

Daniel

[brad131a4]

Daniel I think I see what might be some of the problem in the FI department. It looks to me that you are trying to combine the mechanical and the electrical together. Mechanically the fi on a spider will handle just about any physical mod you can do to the bottom end and be better on the street than carbs for daily driving.This is where the electrical part of the fi comes into play as far as in tuning of the air/fuel mixture and other parameters over carbs. I've had a few interesting email conversations with Guy about some of the things talked about here and most of what I understand from Guy is pretty much what pope was saying about cfm and how much you need to get in and out to get to the desired hp and torque you want. I will say if you want something interesting to read just ask Guy a question and you will get back just about every type of way and reason its done what is the best and what he thinks the best would be for you and your application. I just wish I had bought one of his books back in the day when they were available great stuff .

[pope]

Hey Daniel,
Standard engine formula. CFM= (CID X RPM X .5 X .80) divided by 1728

.5 because only two of the four cylinders are receiving air at a time.
.80 because that is the efficiency of a 8V engine, 16V is usually around .88
1728 coverts cubic inches to cubic feet


CFM = (121 X 6000 X .5 X .80) divided by 1728 = 168 CFM 8 valves
CFM = (121 X 6000 X .5 X .88) divided by 1728 = 184 CFM 16 valves
CFM = (121 X 6000 X .5) divided by 1728 = 210 CFM 100% max efficiency (dream land)

You say that you know someone with 230 hp on a 2.0? I'll bet that they have added cams that can rev into the 8000 range (I'm talking about 6000 redline) and very high compression pistons and I also believe that they rebored the block to use larger pistons and it is therefore not a 2.0 anymore. Very race typical. I'll also bet he changes out his bearings after every race. I'll also bet that he added a 16 valve head to top it off. So we are not even talking about the same engine anymore.

Fuel injected engines are much more difficult to increase. The Bosch system really keeps tabs on you. Turbocharging and Supercharging is perfect for the Bosch systems and can really get you some great HP, without having to do too much to the stock engine.

I use this racing site that has a calculator that estimates the HP from CFM's. It says that 168 cfm's on a 4 cylinder could produce 172 hp. When I plug in 100cfm it says 102hp ( which is stock on the FI Spider). I am looking for a formula to prove them right, but I just dont know. It almost seems to be a 1:1 ratio. I know the CFM calculations above are correct though.

[bandit]

Hi pope


Thx for reply ! The 230 TC wasnt a 16v head but a 8 with 14 to 1 CR yes big valves and over
sized pistons big Cams ( race engine ) they didnt need to change the bearings every race but
how often i'm not sure . They had a trick to getting the CR up 14 to 1 as far as i know no one
else has been able to get that out of a Fiat TC not even croft . It's a neat secret i guess
and i feel lucky enough to know about it .
I haven't played with Turbos but know people who have and they would agree with you about the
FI being a good system to use after a few Mods .


Daniel