We had the carbed volvo engine on the dyno and it made 25bhp less and the torque curve was not as good as the itb engine. This engine came like this from sweden. I assume with some mapping it would be better but i dont have acces to the ignition ecu.
They make a lot of power for a NA 4 pot engine.
However i think with some modifications to the engine it would do another 20bhp more.
Double post
Last edited by Bart; 20-12-2017 at 20:13.
Hi Bart,
OK, this carb engine seems to be off when it comes to power but question is, is this the same spec. as the previous engine on ITB's? I've seen many carb engines making a lot less power than the one fitted with ECU's. Usual because the carb engines where build up around a very small budget and often the ECU engines I had in where build up round a much better budget.
Best to compare both systems on the same engine. Indeed it can be that the carb engine is the same and does make a lot less torque because it was one carbs.
Yes, those Swedish engines do make a lot of power. Nice cylinderheads and very often 3 ltr and even 3,5 ltr.
Originally Posted by Graham
That would be why my mrs car a 106 rallye on bike carbs was so bad on fuel when if was 'off cam'. The cam was massive in it and she always told me the faster she cruised on the motorway the better it was on fuel. I didn't believe this untill i drove the car some distance. She was right. Unless it was over 4.5k it was awefull on fuel.
That's very correct. But it's not only because of the fuel being very rich. Also because when the engine is "off-cam" the engines torque is low. meaning the engine is not werking very effective. It's where the torque is highest the engines is most effective. That's also the reason why I keep telling, please don't use cams to fast in a road engine. It's bad on fuel consumption and does not drive well. And indeed, the faster they run the less consumption up to a point. Usual tuned Beetle engines are no harder on fuel on a motorway running 120 Km/h than when they run 90 !!!!
They are the same spec. We removed the carbs and put the itb and ecu on the engine.
These are 3.0 engines which is the max for reliabilty. We had a 3.4 last year but it vibrates due to bad rod ratio. It makes more power but you have to add more weight which is a step back. Downsizing with similar power would be much better.
It was running Mikuni's?
How much power did it made on ITB's? Unless the whole inlet track is making a total different shape I'm quite sure it should make the same top power on Webers. But if you need to make a short turn before fitting these carbs I can have an influence (sometimes worse, sometimes even better).
Yes its running mikuni's. It made 361bhp on itb and 336bhp on the carbs. I do admit i mapped the itb engine to mbt but the carbed engine has a nira ecu and i cant acces it so it could be the ignition is not spot on.
They both have a small turn at the head before itb/carbs
Sad you could not correct the ignition, not even sure it was needed.
Did you had the chance to change jets in the carbs? Seems like a big difference in power, if the fuel supply was right, this can not only come from the fact it is running carbs, not fuel injection. Maybe the trumpets where different chape or even more in the inlet track. These Mikuni's are open carbs at full throttle with zero restriction from chokes or whatever. It should make the same max power as ITB's. In lower RPM's I can understand the ECU can make better fueling.
I always had the chance I was replacing Webers with throttle bodies (DCOE style). Whole inlet track stayed the same.
No we didnt change anything. We just wanted to compare the engines. Next year another carbed engine will be tested so that would be interesting to see what power this engine makes. I would like to try the 3.4 head and bigger itb on a 3.0. I have the feeling the 3.0 head is restricting the engine.
Sorry again but you say "engines". This means the engine with the carb does have the same spec but was not the engine with ECU?
Did you fitted ECU and carb on one and the same engine, not taken from the dyno? Not in a (different) car on a rolling road ?
Always important to compare at exact the same engine.
Is the difference between fuel injection and carbs because of fuel atomisation ?
No every engine is like that.
i want to push it
You have a point but dont have the money to test it. Btw i know a lot
My S2 106 rallye was exsaclty the same on bike carbs was running a Kent. 292 deg cam
Please note, carburetor tuning problems can cause the same issues. I've never installed any Kent Cam in a Peugeot, can't say it's over the top for the purpose or not. If you carb was incorrect tuned, to rich at lower RPM's, you got the same results. Poor acc. an high fuel consumption.
The carbs where tuned wrong at 1st, way to rich in the low rpm’s took it to somwhere eles, I left with 1 bhp less on the top end but a huge 60bhp more in the midrange, was still horrible if you gave it full throttle off cam
Sad you where not able to make it correct over full line. I don't have much experiences with Bike carbs on cars (CV carbs).
60 Bhp gain and lost 1 at top, that's a good deal.
thats exactly what I thought,
I have just picked up my head today, it has a HT1E cam? having looked its bigger than the HT1
specs are,
power band 3000-7750
cam lift 8.1mm inlet 8.0mm exhaust
valve lift 13.46mm inlet, 12.95mm exhaust
duration 316 deg inlet 300 deg exhaust timing 54/82 76/46
full lift inlet 104 deg ATDC/Exh 104 deg BTDC
lift @ tdc 5.33mm inlet
don't know how much it effects every thing.
not much - it still wont work in your engine
I've always thought the HT1e was slightly softer as the HT1 and latest version should be even softer because it was revised. But I do know that I seldom get the camshaft I've ordered but don't want to start talking about these issues, no one is willing to believe this anyway but the numbers of "wrong grind" cams I got is very high. What data do you have for the original HT1 ?
About this cam data, yes sound like a correct HT1e. I don't like them grind to 104°. It only add more of what you don't want. Yes, it is a good cam but I would not recommend for any car also used on the road and ONLY if you got a super correct ported head, otherwise you will loose a lot of power and torque. These cams need a real working head.
Can you expand on this? Piston to valve clearance at Tdc?not much - it still wont work in your engine
It’s a Jem’s big valve head not a diy job, the cam came with the head, it’s a fresh build that was a spair for a race car, 44.4 inlet and 38.1
If I need to I can buy another better suited cam shaft. I could see if anyone local has a flow bench to test the head.
On Kent cans website the List a ht1 and ht1e
Beware you do need valve cutout's on pistons or your into troubles very soon !!!
On Kent cans website the List a ht1 and ht1e[/QUOTE]
Funny, Kent always told me HT1 was a more aggressive profile compared to the HT1e. Seems not to be the case. But is not the first mistake I've seen from camshaft makers.
Ok thanks I did suspect this, do you know what the max lift at tdc cam be before I run into problems?
Is it as simple to calculate as, head off, turn until I reach the amount of lift at tdc measure how much the valve is sticking past the face of the head and I know the deck height and thickness of the gasket? How much clearance do I need 1mm?
Also you you know how much material can be removed from the pistons? There standard
Kent quoted for you 5,33 mm at TDC (with lobes at 104°). Mine where further apart, must check my data but I do know I was t 5 mm. You need more than 1 mm, I would suggest at least 1,5 for inlet and bit more for exhaust.
Standard Pistons !!!??? HT1e ?? I don't think they will stand for long. I was using DP custom made pistons and they always come with valve pockets.
Kent quoted for you 5,33 mm at TDC (with lobes at 104°). Mine where further apart, must check my data but I do know I was t 5 mm. You need more than 1 mm, I would suggest at least 1,5 for inlet and bit more for exhaust.
Standard Pistons !!!??? HT1e ?? I don't think they will stand for long. I was using DP custom made pistons and they always come with valve pockets.
standard pistons?? forget it!!! you can probably put deep enough cut outs to cope with the cam, but std pistons cant cope with the compression needed to make the cam work properly, so you will end up with the worse of everything, either build with high compression and break the pistons, or run lower compression and have no top or bottom end power, if its a race car use forged pistons, if its not use less cam
standard pistons?? forget it!!! you can probably put deep enough cut outs to cope with the cam, but std pistons cant cope with the compression needed to make the cam work properly, so you will end up with the worse of everything, either build with high compression and break the pistons, or run lower compression and have no top or bottom end power, if its a race car use forged pistons, if its not use less cam
So that cam shafts no good as I’m not in a position where I can build a full engine,
What’s a good cam shaft for what I’ve got???
Road use is not a concern it’s a track car spends 90% of its life on track.
I will have a compression ratio of 10.4:1 if lift at tdc is not to big I could have the head skimmed more to raise the compression, I think there’s just over 1mm before the spark plug is proud of the head. When using a calculator if i went from 44cc head to 38cc that would take the compression to a little over 11.??:1
So that cam shafts no good as I’m not in a position where I can build a full engine,
What’s a good cam shaft for what I’ve got???
Road use is not a concern it’s a track car spends 90% of its life on track.
I will have a compression ratio of 10.4:1 if lift at tdc is not to big I could have the head skimmed more to raise the compression, I think there’s just over 1mm before the spark plug is proud of the head. When using a calculator if i went from 44cc head to 38cc that would take the compression to a little over 11.??:1
valve lift at tdc isnt your problem, if you go over 10.5 and use it hard on track you WILL break the pistons, you need forged pistons or a cam which will work with what you have, id suggest an RL31
Never found out what cam it was tbh but i was in my friends 1400 xsi when he bought the car it was flat untill 5k/5250k it pulled like a train then it would hit the limiter at 6.5k. It was pants! But coupled with a 1.6 8v engine bike crabs and a full exhasut system it pulled from 3.5k to just under 8k. Was a brilliant motor!
Mine pulled well from 3k but came alive at 5k and would sing all the way to 8500, was a standard bottom end and I built it about 8 years ago and last I heard the engine was still going, it had 105k miles on the bottom end and box when I sold it. I’ve chased an engine like that since I sold it.
Listen to her sing
https://youtu.be/DMCMB0h0RlQ
You can never go wrong with an RL31, BP300 (piper) or Newman 4,75 camshaft. These are approx the same cams (if not exact the same but you can never see because they all use different followers). I prefer to have them grind at 112° but if you ask 112° to a camshaft grinder, please check after you receive the cam because you can get the most funny cams ever seen. So that's the downside of asking a simple thing to a camshaft manufacturer.
These cams always work, even if the head is a little bit less perfect it will still not let down. Faster cams will produce LESS power if you do it wrong. They more relay on the worlds most perfect tuned inlet track. If not, they fail dramatically.
Standard pistons also have to wide rings and soft ring lands. After a few hours the ring groove is getting wider and rings will start to flutter, finally fail. It's ok for short races like rallycross or autocross for a very short time.
If it's a jems head get a pic of the short turn on inlet to make sure it's finished correctly . If comp is at 10.4 you would be at your limit with a the rl31
This thread seems to have carried over from another one on here regarding compression. You are going to have to skim the cylinder head to death to try and get a 38cc combustion chamber. After you have skimmed it your valves are going to be even closer to your pistons at tdc. Your pistons are too far down your bores to be ideal, I would recommend having the block skimmed by 20 thou. Even by doing that you are moving the valves closer to your pistons.
The easiest way to do a quick check on your head whilst it's off the car is to get the inlet valve open at 5.5 mm on the HT cam on over lap and put a straight edge across the chamber face and measure how much the valve will open before touching the straight edge. Whatever clearance you have there along with the gasket thickness will give you a rough idea. remember to do the same with exhaust valve. Please note this is only a rough guide to give you some idea where you are up to with piston clearance and should not be taken as gospel.
I have seen Race cams before in engines with too lower compression and they are very disappointing on power, go for a milder cam for now until the budget allows to go for forged pistons.
Thanks for this, I have seen a previous post from graham when he flown tested one, I will get some pictures and post them
Posting Permissions
Reply With Quote
Bookmarks